Bell, 22, was a rising star, having won the 2013-14 Brisbane Jockey's Premiership in his first senior season.
How he fell is unclear. One report says he was locked out and was trying to climb up to his 12th-floor property.
Racing Queensland's Acting CEO Ian Hall said Bell would be remembered as a "brilliant rider".
"It is tragic when someone so young and with so much talent is taken away from us," Mr Hall said.
"Racing Queensland joins with the entire racing community in offering our sincerest condolences to Tim's family and his partner Heidi."
The Australian Broadcasting Corporation said the jockey tripped and fell from his apartment on Tuesday night.