Mom's Knife

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Removed in Afterbirth †Item icon
Added in Afterbirth †Item icon
Item altar
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Tear appearance
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Devil Room Devil Room
Treasure Room Treasure Room
Greed mode only Devil Room Devil Room
Greed mode only Treasure Room Treasure Room
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Added in  Afterbirth(page 1, column 11, row 6)
Removed in Afterbirth(page 2, column 1, row 2)
Mom's Knife Defeat Satan as IsaacMom's KnifeMom's Knife

Mom's Knife is a Special unlockable passive item.


  • Isaac's tears are replaced by a knife that pierces enemies and can travel through obstacles. Holding down the fire button increases its range and power.
    • The knife can hurt enemies while Isaac is holding it.
    • The knife deals 2x Isaac's damage while held and 6x damage at the furthest possible point of its arc, regardless of the actual maximum range stat.


  • The knife can be held and fired diagonally. Firing the knife diagonally requires a frame perfect input. However, this can be done easily with a controller's analog stick or with Added in Afterbirth †Analog Stick Analog StickAnalog Stick Icon.png+0.3 tears up. Allows Isaac to fire tears diagonally..
  • The knife will not work in challenges with the Blindfolded effect.


  • 20/20 20/2020 20 Rebirth Icon.pngGrants double shot. / Conjoined / The Inner Eye The Inner EyeThe Inner Eye Icon.pngGrants triple shot but decreases tears. / Mutant Spider Mutant SpiderMutant Spider Icon.pngGrants quadruple shot but decreases tears.: Isaac holds only one, but shoots multiple knives at their typical spread.
  • Brimstone BrimstoneBrimstone Rebirth Icon.pngTears are replaced by a laser beam that pierces through all enemies and obstacles in its path and deals high damage. Can only be fired after a short charge-up period.: Firing the knife also shoots a barrage of knives that goes across the screen, with each knife doing 80% of Isaac's damage. The longer the charge, the more knives are added. This effect does not work with Azazel's default mini brimstone. The brimstone-knives do not benefit from A Lump of Coal A Lump of CoalA Lump of Coal Icon.pngThe more distance tears travel, the more damage they will do..
  • Chocolate Milk Chocolate MilkChocolate Milk Icon.pngGrants charged tears that deal greater damage when fully charged.: Tears up instead of additional damage or charge effects. Knife will also be colored brown.
  • Added in  AfterbirthContinuum ContinuumContinuum Afterbirth Icon.png+2.25 Range Up. +1.5 Tear Height. Isaac's tears travel through walls and appear out of the opposite wall. Isaac's tears also travel over rocks and objects.: The knife can now travel through walls and appear out of the opposite wall but will still have the boomerang effect.
  • Added in  AfterbirthDiplopia DiplopiaDiplopia Icon.pngOne time useDuplicates all pickups and item pedestals in the room.: Shoots two knives simultaneously without reducing fire rate.
  • Fire Mind Fire MindFire Mind Icon.pngGrants flaming tears that deal burning damage over time. Tears have a chance to explode on impact with an enemy, which creates a fire at the location of the explosion.: Still applies burning but no longer explodes.
  • Added in Afterbirth †Flat Stone Flat StoneFlat Stone Icon.pngTears bounce off the floor. Tears that hit an enemy after bouncing deal splash damage to all nearby enemies for 25% of Isaac's tear damage.: Knife bounces as it flies away from Isaac, each bounce splash causing Isaac's base damage.
  • Added in Afterbirth † The Forgotten: The knife attaches to the Forgotten's bone club, forming a scythe with a larger swing and higher damage.
  • Added in Afterbirth †Ghost Pepper Ghost PepperGhost Pepper Icon.pngAdds a chance to shoot a fire that damages enemies and remains in place until it deals enough damage or the room is left.: The flames can shoot from Isaac while holding the fire button.
  • Gnawed Leaf Gnawed LeafGnawed Leaf Icon.pngAfter standing still and not shooting for a short time, Isaac turns invincible until he moves or shoots.: The held knife can damage enemies while Isaac is invincible.
  • Godhead GodheadGodhead Icon.pngIncreases damage and range while reducing tears and shot speed. Grants homing tears and tears gain a damaging halo.: The knife homes in on enemies, but it does not gain a damaging halo.
  • Guppy Transformation: Knife hits will rarely spawn an attack fly.
  • Added in Afterbirth †Haemolacria HaemolacriaHaemolacria Icon.pngTears are now fired in an arc. Upon hitting the floor, an obstacle, or an enemy, they burst into many smaller tears in all directions. Increases tear delay.: Haemolacria works at the same time with Mom's Knife, with Haemolacria's fire rate resulting in longer charging.
  • Homing Tears: Knives home in on enemies and colors the knife purple. It will stick on enemies for a second and make small lunges towards other enemies.
  • Ipecac IpecacIpecac Icon.pngReplaces tears with explosive and poisoning projectiles fired in an arc from the mouth.: Knife turns green, may poison monsters that hit it, and removes Ipecac's damage increase.
    • Added in Afterbirth † Also adds +4 damage.
  • Lost Contact Lost ContactLost Contact Icon.pngEvery tear has a small shield which will allow it to block one enemy projectile.: The knife will block bullets, even when held.
  • The Ludovico Technique The Ludovico TechniqueThe Ludovico Technique Icon.pngInstead of firing tears, Isaac controls one floating tear that hover over obstacles. This tear deals constant damage when held in place over an enemy.: Isaac controls a floating knife that deals 2x Isaac's damage. Tears stat is ignored and damage is dealt at a rate equivalent of 5 tear delay.
    • The Ludovico Technique + any multi-shot item: Isaac controls a floating knife surrounded by additional rotating knives.
    • The Ludovico Technique + Lost Contact: Floating knife loses almost all ability to block bullets, with a tiny area around the hilt that can stop shots.
    • The Ludovico Technique + Loki's Horns Loki's HornsLoki's Horns Icon.pngGives a random chance for projectiles to fire in all 4 cardinal directions.: Loses Loki's Horns effect; Isaac controls only one floating knife.
  • Added in  Afterbirth Monstro's Lung Monstro's LungMonstro's Lung Icon.pngIncreases damage and grants a charged shot that fires multiple tears in the same fashion as Monstro.: Fires a cluster of 3-5 knives at maximum charge, each dealing 2x damage.
  • Proptosis ProptosisProptosis Rebirth Icon.pngTears start out massive with high damage, and then shrink down and become weaker over a short range.: The Knife deals double damage regardless of range.
  • Strange Attractor Strange AttractorStrange Attractor Rebirth Icon.pngPickups, trinkets, and monsters are magnetically attracted to Isaac's tears.: Enemies are pulled towards the knife. The effect is minor while not firing and much stronger while the knife is launched.
  • Tammy's Head Tammy's HeadTammy's Head Icon.png1 roomsShoots 10 tears in a circle around Isaac, which retain the damage, shot speed, and special effects (such as poison) of Isaac's tears.: Fires 10 knives in a circle around Isaac, dealing massive damage.
  • Added in  AfterbirthTech X Tech XTech X Icon.pngTears are replaced with laser rings that pierce through enemies and deal damage to enemies within them. Can be charged to increase the size of the ring.: Both fire normally.
  • Technology 2 Technology 2Technology 2 Icon.pngDecreases damage and replaces right eye tears with a unlimited range, piercing laser which fires continuously.: While charging Mom's Knife, Technology 2 will still fire.
  • Trinity Shield Trinity ShieldTrinity Shield Icon.pngIsaac gains a shield that protects him from enemy shots.: Blocks bullets in the direction the knife is held, giving enough protection to walk up to and melee enemies, or just to safely shoot the knife.
  • Unicorn Stump Unicorn StumpUnicorn Stump Icon.png1 roomsUpon use, grants invulnerability and increased speed for five seconds, but removes the ability to shoot tears. and other invincibility items: Even though the knife cannot be fired, the knife will deal damage while Isaac is invincible.


  • Anti-Gravity Anti-GravityAnti-Gravity Icon.png-2 Tear Delay. Tears float in position until firing ceases, after which they will fly off in the direction they were shot in.: Only tear delay down applies.
  • Added in Afterbirth †Apple! Apple!Apple! Icon.pngIncreases tears. Adds a chance to fire a high-damage razor blade. / Added in Afterbirth †Euthanasia EuthanasiaEuthanasia Icon.pngAdds a chance to fire needles. If a needle kills an enemy, it bursts into more needles. / Tough Love Tough LoveTough Love Rebirth Icon.pngAdds a chance to shoot a tooth instead of a tear, which deals greater damage than regular tears.: No chance of higher damage or instant kills.
  • Added in Afterbirth †Compound Fracture Compound FractureCompound Fracture Icon.pngIncreases range. Tears turn into bones, which shatter into 1-3 bone shards upon hitting an enemy or obstacle. / Cricket's Body Cricket's BodyCricket's Body Icon.pngGrants -1 Tear Delay and reduces Range. When tears hit an object or deplete their range, they spawn 4 smaller tears, whose Range and Damage scale with Isaac's. / The Parasite The ParasiteThe Parasite Icon.pngIsaac's tears split in two when they hit something.: Only stat effects, if any, apply without splitting.
  • Cursed Eye Cursed EyeCursed Eye Icon.pngGrants charged tears that can be fired in a tight burst of four. Getting hit while charging will teleport Isaac into another room.: Overridden by Mom's Knife.
  • Dr. Fetus Dr. FetusDr. Fetus Icon.pngTears are replaced by bombs that benefit from bomb-enhancing effects and slide for a fixed time after being fired.: Overridden by Mom's Knife.
    • Added in  Afterbirth Both the knife and the bombs fire normally.
  • Epic Fetus Epic FetusEpic Fetus Icon.pngIsaac's tears are replaced with guided missiles, like those used by the Doctor's Remote.: Overridden by Epic Fetus.
    • Added in  Afterbirth Each explosion shoots 10 knives in a circle from the point of impact.
  • Added in  AfterbirthExplosivo ExplosivoExplosivo Icon.pngIsaac's tears have a chance to stick to enemies and explode.: Overridden by Mom's Knife.
  • Added in Afterbirth †Eye of Belial Eye of BelialEye of Belial Icon.pngGrants piercing tears. After piercing one enemy, tears start homing and deal double damage.: Overridden by Mom's Knife.
  • Added in  AfterbirthHoly Light Holy LightHoly Light Icon.pngIsaac has a random chance to fire a Holy tear, which, when it hits an enemy, will spawn a Crack the Sky-style light beam on the same enemy, dealing damage.: Overridden by Mom's Knife.
    • Added in Afterbirth † Holy Light can trigger on both held and thrown knives.
  • Added in Afterbirth †Lachryphagy LachryphagyLachryphagy Icon.pngIsaac's tears decelerate as they travel. Upon stopping or hitting an obstacle, they burst into 8 tears in all directions. Tears can be fired into other tears to feed them, increasing their damage.: Overridden by Mom's Knife.
  • Added in Afterbirth †Little Horn Little HornLittle Horn Icon.pngAdds a chance to fire a piercing tear that instantly kills any enemy that it touches.: Overridden by Mom's Knife.
  • A Lump of Coal A Lump of CoalA Lump of Coal Icon.pngThe more distance tears travel, the more damage they will do.: No effect on the knife regardless of range.
  • Added in  AfterbirthMarked MarkedMarked Icon.pngIsaac will now fire tears automatically directed at a red target on the ground which is controlled by the player. This allows for a full 360 degree tear firing radius. Can be overridden by other tear modifiers such as Mom's Knife or Brimstone.: Only tears up and range up apply.
  • Monstro's Lung Monstro's LungMonstro's Lung Icon.pngIncreases damage and grants a charged shot that fires multiple tears in the same fashion as Monstro.: Overridden by Mom's Knife.
    • Added in  Afterbirth Firing a knife causes several other knives to shoot out at random directions.
  • My Reflection My ReflectionMy Reflection Icon.pngGives Isaac's tears a boomerang effect, and increases range and shot speed.: No effect.
  • Mysterious Liquid Mysterious LiquidMysterious Liquid Icon.pngTears leave a small, short lasting pool of creep on impact or when their range is depleted.: Overridden by Mom's Knife.
    • Added in Afterbirth † The Knife leaves creep trails while fired.
  • Added in Afterbirth †Pop! Pop!Pop! Icon.pngReplaces Isaac's tears with eyeballs that can bounce off of each other. The eyeballs are not limited by range, and will instead dissipate when they stop moving or when hitting an enemy or obstacle.: Overridden by Mom's Knife.
  • Proptosis ProptosisProptosis Rebirth Icon.pngTears start out massive with high damage, and then shrink down and become weaker over a short range.: Damage is doubled and no damage decrease with distance.
  • Rubber Cement Rubber CementRubber Cement Icon.pngTears bounce off walls, enemies, and environmental objects.: Overridden by Mom's Knife.
  • Technology TechnologyTechnology Icon.pngReplaces tears with a piercing laser with unlimited range.: Overridden by Mom's Knife.
    • Added in  Afterbirth Both the knife and the laser fire normally.
  • Tiny Planet Tiny PlanetTiny Planet Icon.pngRange up and makes shot tears revolve around Isaac until they drop.: Knives go in a spiral around Isaac; the longer the knife is charged, the bigger the spiral. Not recommended, as this makes Mom's Knife almost impossible to aim.
  • Added in Afterbirth †Trisagion TrisagionTrisagion Icon.pngTears are replaced with piercing white blasts of light.: Overridden by Mom's Knife.

In-game Footage


  • Added in  Afterbirth This item is used in Challenge #26 (I RULE!).
  • In the original Binding of Isaac, buying the item from the Devil Room cost 1 heart container instead of 2.
  • The description of the item is a possible reference to the sniper's dialogue in Team Fortress 2.


 PC  Added in Afterbirth † 8CKM J108 (Treasure room adjacent to spawn) Hard mode only

 PC  Added in Afterbirth † 6PG9 7RK3 (Treasure room up and to the right one room from spawn)

 PC  Added in  Afterbirth DVNV YV9Y (Treasure room adjacent to spawn)

 PC  JW43 H8EK (Treasure room adjacent to spawn)

 PC  1M9E Y1G1 (Treasure room adjacent to spawn)

 PC  P8SE A9JW (Treasure room adjacent to spawn)

 PS4  S63T 434W (Treasure room adjacent to spawn)

 Switch  Greedier mode only JZCL 97JE (First Golden Treasure Room)

 3DS  Z3SL DS3W (hard; first floor treasure room)


Bug Bug! The Blindfolded condition also applies to the knives fired by Tammy's Head, and prevents it from working.

Isaac  Unlocks Isaac Unlocks Isaac  Unlocks
Added in  Afterbirth Added in Afterbirth †
Mom's KnifeMom's KnifeDefeat Satan as IsaacThe D20The D20Defeat ??? as IsaacIsaac's HeadIsaac's HeadComplete the Boss Rush as IsaacIsaac's TearsIsaac's TearsDefeat Isaac as IsaacMissing PosterMissing PosterDefeat The Lamb as IsaacLost BabyLost BabyDefeat Mom's Heart on hard mode as Isaac Fart BabyFart BabyDefeat Hush as IsaacLil' ChestLil' ChestDefeat Ultra Greed as IsaacCry BabyCry BabyDefeat Mega Satan as IsaacBuddy BabyBuddy BabyEarn all hard mode completion marks as IsaacI RULE!I RULE!Defeat ??? or The Lamb for the 1st time, and defeat Satan as Isaac D InfinityD InfinityDefeat Delirium as IsaacD1D1Defeat Ultra Greedier as Isaac
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