The man in his 20s collided with the cab just before 5pm on Victoria Ave near Little Graham St in Albert Park.
Paramedics were on scene soon after the accident but were unable to save the man and he died on scene.
Police believe the cab driver may have performed a u-turn when the motorcyclist collided with him.
“There are not details yet as to whether he was able to do a u-turn in that location,” police spokeswoman Creina O’Gready said.