Lachlan Young, 23, initially denied he killed his former girlfriend Hannah McGuire in April 2024, arguing it was a spontaneous incident.
But after eight days of evidence in the Victorian Supreme Court, he conceded he strangled her and then burned her body in remote bushland.
At his plea hearing on Monday, Young's barrister Glenn Casement accepted his client's plea was not early but said it could go towards mitigating his sentence.
Young was an immature and troubled 23-year-old but his plea demonstrated he was remorseful for his actions, Mr Casement said.
"Even though it was late, he is still a young man and there is an emerging acceptance of responsibility," the barrister said.
As part of his plea, Young told prosecutors exactly how he killed Ms McGuire.
He admitted he pushed Ms McGuire onto the bathroom floor of their Sebastopol home during an argument and strangled her about 2.30am on April 5.
He then shoved her body into the footwell of her Mitsubishi Triton, drove it to remote bushland and set the vehicle alight.
As he left the scene, Young used Ms McGuire's phone to send messages to her mother Debbie, claiming she was going to take her life.
He then transferred $2000 from Ms McGuire's bank account to her mother and $5000 to himself.
"There's no escaping in this case the series of callous and heartbreaking acts that occurred in the aftermath of the offending," Mr Casement told the court.
"They were all doomed to fail and amateurish in many respects."
Mr Casement will make further submissions on sentence on Tuesday before crown prosecutor Kristie Churchill addresses the court.
Dozens of Ms McGuire's family members, friends and colleagues filled the Ballarat courtroom on Monday as victim impact statements were read out.
Ms McGuire's mother Debbie described her daughter as her light and best friend, while Hannah's father Glenn said he would live with anger, grief and guilt for the rest of his life.
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