The 'All For You' star was due to perform in Melbourne on Wednesday, Thursday and Saturday as part of her 'Number Ones' tour, but has opted to reschedule the gigs for one single concert on November 3 at the city's Rod Laver Arena.
Jackson explained that she needed to be with her family as Murray's defence team begin presenting its case this week.
"When I planned these shows, the [trial] schedule in California was completely different. After talking with my family last night, I decided we must be together right now... This saddens me in so many ways," she said in a statement to The AP.
Dr Murray stands accused of killing Michael by administering a lethal dose of propofol on June 25, 2009.
Last week, a propofol expert testified that Michael had more drugs in his system at the time of his death than Murray claimed to have given the late popstar.
> Michael Jackson trial sleep expert: 'Treatment a recipe for disaster'
> Michael Jackson 'was healthy before he died', Conrad Murray jury hears
Watch Janet Jackson and the Jackson family enter the court during the first week of Dr Conrad Murray's trial below: