Born in Toronto, Bob Walker lived in Kitchener and London before his family finally settled down in Ottawa, Ontario. He took art classes at New York's St. Lawrence University, but decided that a general liberal arts degree wasn't what he wanted. A family friend steered him towards the animation department at Sheridan College in Oakville, Ontario. After completing three years at Sheridan, Walker was hired as an apprentice at Atkinson Film Arts in Ottawa, where he worked on animated productions such as the television series The Raccoons. After five years with Atkinson, he learned that Disney was opening a new studio in Florida and needed staff. He jumped at the chance, coming on board in April 1989 just as the new studios opened, and began as a layout artist on the Roger Rabbit short Roller Coaster Rabbit. He eventually worked his way up to being the head of layout at the Florida studio, working on features such as Rescuers Down Under (1990), Beauty and the Beast (1991), Aladdin (1992), The Lion King (1994), Mulan (1998) and Lilo & Stitch(2002).
Walker and co-director Aaron Blaise (with whom he'd worked on many Disney features) made their feature film directing debut with Brother Bear (2003), featuring the voices of Hollywood stars such as Joaquin Phoenix, Michael Clarke Duncan, Rick Moranis and Dave Thomas.