The video, obtained by US outlet CNN, appears to depict Combs wearing only a white towel chasing his former partner, real name Casandra Ventura, and kicking her on the ground.
The footage also appears to show the US music mogul dragging Ventura, and throwing a vase in her direction.
Sean Diddy has apologised for the "inexcusable" beating of his girlfriend, singer Cassie. (AP PHOTO)
In a video statement posted to Instagram, Combs said his behaviour was "inexcusable" and that he was "disgusted" by it.
His apology continued: "It's so difficult to reflect on the darkest times in your life, but sometimes you got to do that.
"I was f***** up - I hit rock bottom - but I make no excuses.
"My behaviour on that video is inexcusable. I take full responsibility for my actions in that video.
"I was disgusted then when I did it. I'm disgusted now. I went and I sought out professional help. I got into going to therapy, going to rehab.
"I had to ask God for his mercy and grace. I'm so sorry. But I'm committed to be a better man each and every day. I'm not asking for forgiveness. I'm truly sorry."
The video has been dated March 5, 2016, and seems to match a description of an incident at the InterContinental Hotel in Los Angeles in a now-settled lawsuit originally filed by Ventura in November.
The court document said: "In or around March 2016, during an FO at the InterContinental Hotel in Century City, Los Angeles, Mr Combs became extremely intoxicated and punched Ms Ventura in the face, giving her a black eye."
Ventura claimed she was a victim of rape and violent behaviour during their decade-long relationship in the lawsuit, which was settled a day after it was filed at a New York federal court.
A statement from Douglas H Wigdor, lawyer for Ventura, in response to the video footage said: "The gut-wrenching video has only further confirmed the disturbing and predatory behaviour of Mr Combs.
"Words cannot express the courage and fortitude that Ms Ventura has shown in coming forward to bring this to light."
Combs has since been named as a defendant in several sexual abuse lawsuits, and in March his properties in Los Angeles and Miami were raided by federal authorities in a reported sex trafficking investigation.
The Los Angeles County District Attorney's Office said on Friday that the assault captured in the video would be too old to prosecute if it occurred in 2016 due to the statute of limitations.
"We are aware of the video that has been circulating online allegedly depicting Sean Combs assaulting a young woman in Los Angeles," it said in a statement.
"We find the images extremely disturbing and difficult to watch.
"If the conduct depicted occurred in 2016, unfortunately we would be unable to charge as the conduct would have occurred beyond the timeline where a crime of assault can be prosecuted.
"As of today, law enforcement has not presented a case related to the attack depicted in the video against Mr Combs, but we encourage anyone who has been a victim or witness to a crime to report it to law enforcement or reach out to our office for support from our Bureau of Victims Services."
