After graduating from the Classical Animation Program at Sheridan College in Oakville, Ontario, Ranieri went to work for Atkinson Film-Arts animation production studio (in Ottawa, Ontario).

On his next film, Ranieri was promoted to supervising animator on the character of Wilbur in The Rescuers Down Under.

[3] While Ranieri is regarded as one of the modern-day masters of hand-drawn character animation (especially excelling in subtle dialogue scenes and facial expressions) he also successfully made the switch to animating in CG on films such as Chicken Little, Meet the Robinsons and Bolt.

On April 6, 2013, The Walt Disney Company announced that Ranieri, along with eight other animators working at Walt Disney Animation Studios, had been laid off in an effort for the company as a whole to cut costs.

Ranieri won the Outstanding Individual Achievement In Animation award in 2021 at the 73rd Primetime Creative Arts Emmy Awards as Lead Character Layout for The Simpsons episode Wad Goals.