The couple were said to be caught up in a heated row in their Los Angeles penthouse on December 15 in 2015.
Depp, 47, made the admission while he gave evidence at London’s High Court on the third day of his libel case against News Group Newspapers.
The High Court heard a recording shortly after the alleged incident where Johnny appeared to say he only headbutted her in the “f**king forehead” so he couldn’t “break a nose”.
In the recording, Amber could be heard saying: “You had been screaming … it’s the end-all-be-all in the sort of offensive thing.
“You can throw a punch but yet screaming’s OK. You can headbutt somebody who’s screaming but don’t scream.”
Depp seemed to say: “I headbutted you in the f**king …”
Amber interrupted him to add: “I couldn’t believe you did that.”
The actor then said: “… forehead. That doesn’t break a nose.”
In his own words, Depp claimed Amber was “swinging wildly at me” when he referred to the recording.
He added: “This injury that she would’ve suffered is not consistent with the photographs that she has given to the court.
“She was swinging wildly at me, and I … from behind, as I was walking away from the argument to my office, she was hitting me in the neck, ear, back, everything.
“I turned to cover my head and she was swinging quite wildly so the only thing I could do in that situation was either to run or to try to get hold of her, to get my arms around her to stop her flailing and punching me, so I did so, as I did so it seems there was a collision.”
Depp used his arms to show how he claimed to have taken hold of Amber while she was “kicking and moving”.
He added: “That is the only collision and the only potential injury that Ms Heard could have had, there is no way I did as she said and broke her nose.”
Photographs of Heard and Depp’s alleged injuries were shown to court.
NGN’s barrister Sasha Wass QC grilled Depp over why he hadn’t mentioned “accidentally” headbutting his ex wife before.
Depp said he used the word “headbutt” because it was the same word used by Heard.
Johnny replied: “Had I read the entire statement after the lawyers had drafted it, I would have found that missing piece. I didn’t read all those things … and I trusted my attorneys had taken my statement and put it on the record.”
Depp has denied he was ever violent towards his ex-wife and has accused her of abusing him during their marriage.
Lawyers for NGN are defending their case based on Heard’s 14 allegations of abuse, which include claims of bust-ups between 2013 and 2016.
The actor has argued his ex-wife was abusive towards him during the marriage, which collapsed in 2016.
The case continues.