The New South Wales Supreme Court jury delivered its guilty verdict on Tuesday, setting the 36-year-old up for being sentenced at a later date.
Hachem, from Hurstville Grove, had always denied murdering the 30-year-old on January 4.
Her body has never been found.
Hachem and Ms Baker had known each other for about 15 years and were said by the Crown to have been in an “intermittent intimate relationship”.
The prosecutor alleged Hachem was the last person to see her alive and the only rational explanation was that she was dead and he was responsible for her death.
In his closing address, defence barrister Daniel McMahon argued that the jury could not rule out suicide.
Relatives reported the TAFE worker missing on January 5 after a friend said she dropped her off at her Parramatta home in the early hours of the day before.