The actress told lawyers she did not fear her partner would stab her with the blade. Depp's attorney Camille Vasquez yesterday asked the actress about the knife she bought him for his birthday in 2012.
It was at this time she claims she began suffering physical abuse at his hands.
Ms Vasquez asked: "It was during this cycle of violence that you gave Mr Depp a knife?"
Heard, 36, replied: "I gave him a knife." She added: "I wasn't worried he was going to stab me with it."
Jurors were shown the blade.
Depp, 58, is suing his ex-wife for libel over a 2018 article she wrote in The Washington Post, which his lawyers say falsely implies he physically and sexually abused her while they were together.
Ms Vasquez later played an audio recording of a fight between the couple in which both appeared to ridicule the other's acting career.
On the recording, Heard said: "You're a joke. You're a joke."
Depp said: "Your jealousy is so tragic."
Later, Heard denied hitting her ex-girlfriend Tasya van Ree, and pulling off her necklace, at Seattle airport in 2009. She was not prosecuted over this claim.
The hearing in Fairfax, Virginia, continues.