Mom's Knife is an unlockable passive item in The Binding of Isaac.

Replaces Isaac's tears with a knife that pierces through enemies and can travel through obstacles.

Holding down the fire button increases the knife's range and power.

The knife deals 2x Isaac's damage 20 times per second while held, and 6x Isaac's damage at about 1/3 full charge. Damage quickly drops to 2x Isaac's damage when returning regardless of charge. Further charging only increases the maximum range.

Can be fired diagonally by holding down 2 firing buttons at once.

This page shows the latest information as of the new Repentance+ (Online Co-op) DLC.
To see information about this item for the previous Repentance version, check this page instead.

Defeat Satan as Isaac.

This item contributes towards the Yes Mother? transformation. Collecting 3 items from this set will give Isaac a stationary knife that trails behind him and deals 2x contact damage.

Mom's Knife can be found in the following item pools:

The following tags are applied to this item:

The following special synergies and interactions for Mom's Knife have been documented.

* Note that not all possible synergies and interactions are listed here.

Below is the Internal Item Description as shown in-game.
Note that some stat changes are not displayed here. Please see the main description for the full effects.

Mom's Knife

• Replaces Isaac's tears with a knife
• The knife can be charged and thrown, or held and used as a melee weapon at close range
• Abyss: x1 knife locust 2x Isaac's damage

• Check out the item description on the external Isaac Wiki.