Mark Sheridan Waden was charged after the disappearance of Priscilla Brooten, a 46-year-old US citizen who was living in Australia without a valid visa.
The 50-year-old was found guilty by a jury on Tuesday after weeks on trial in Brisbane Supreme Court. He faces a mandatory life sentence.
"It wasn't me," Waden said when the jury handed down its verdict on its second day of deliberation.
The prosecution alleged he killed Ms Brooten at the home they shared in Brisbane's north, making up stories about why she suddenly disappeared.
They included saying she left him for another man, was on the run from authorities or was living under an assumed identity.
Within weeks of Ms Brooten's disappearance Iin July 2018, Waden invited his new love interest to his home and presented the missing woman's clothes and make‑up as gifts, the court heard.
The day after the 46-year-old vanished, he arranged for a trench to be dug and work to be carried out on a retaining wall at his Bracken Ridge property, telling contractors the council was "on his back".
In May 2019, the court heard there was a flurry of activity at the home after police visited, with the hiring of a self‑drive excavator, the purchase of tarpaulins and rope, and trips to a rubbish tip.
"It is not known when or where exactly Mr Waden disposed of Ms Brooten's body," crown prosecutor Andrew Walklate told the jury.
"However, he may have disposed of her remains at the Nudgee dump."
The prosecution case was entirely circumstantial, built on phone tower data, car movements, Waden's alleged lies to friends, students and authorities, and the backyard excavation.
Defence barrister James Godbolt described it as "conjecture and speculation", arguing there was no body, identified cause of death or forensic evidence tying Waden to murder.
He was being re-tried for the murder after his first trial was aborted earlier in June due to juror misconduct.
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