Video testimony by Dr Laurel Anderson was played for jurors on the third day of the $50m (£38m) defamation trial in Virginia.
Mr Depp has sued his ex-wife over a story she wrote in which she described herself as a victim of domestic violence. He denies any abuse.
Ms Heard filed a $100m counterclaim.
In testimony recorded in February and played for jurors on Thursday, Ms Anderson said she had seen the famous couple for several therapy sessions between October and December 2015. Ms Heard filed for divorce in May 2016 after just 15 months of marriage.
The psychotherapist described a volatile dynamic between Mr Depp and Ms Heard, with both threatening to walk out of sessions amid arguments.
In sessions without Mr Depp present, Ms Anderson said, Ms Heard reported physical assault at the hands of her then-husband. On one occasion Ms Heard came to her office with several small bruises on her face, she testified.
On more than one occasion Ms Heard initiated violent interactions in an effort to prevent Mr Depp from leaving, Ms Anderson said.
"It was a point of pride to her, if she felt disrespected, to initiate a fight," Ms Anderson told jurors. "If he was going to leave her to de-escalate from the fight, she would strike him to keep him there, she would rather be in a fight than have him leave."
Ms Anderson said that Mr Depp was often interrupted by Ms Heard during the therapy sessions.
"Ms Heard had a jackhammer style of talking," the clinical psychologist said. "She was very amped up. He had trouble talking at a similar pace. He was cut off a lot."
Ms Anderson testified to both Ms Heard and Mr Depp's family history of domestic violence. Ms Heard was beaten by her father, she said, and Mr Depp was beaten by his mother.
Mr Depp had been "well controlled" for decades before meeting Ms Heard, Ms Anderson said, and did not engage in violence with past partners. "With Ms Heard, he was triggered. They engaged in what I saw as mutual abuse."
At issue in the trial is Ms Heard's 2018 opinion piece in the Washington Post, describing herself as a "public figure representing domestic abuse". Mr Depp says the article - which does not mention him by name - is defamatory and derailed his career.
Jurors have so far been presented with duelling accounts of Depp and Heard's relationship.
Ms Heard's team has portrayed Mr Depp as a physically and sexually abusive partner prone to drug and alcohol binges.
Mr Depp's team has presented Ms Heard's claims of domestic violence as a "hoax" and a calculated strategy to ruin his reputation.
Also on Thursday, a former personal assistant to Ms Heard, Kate James, testified about what allegedly happened when she asked her then-boss for a salary increase.
Ms James said: "She [Ms Heard] leapt up out of her chair, put her face approximately four inches from my face. She was spitting in my face, telling me how dare you ask me for the salary you're asking for."
The trial, expected to last at least six weeks, is being broadcast live and will involve a number of high-profile witnesses, including James Franco, Paul Bettany and Elon Musk