Walker poured in eight points in the extra frame, surpassing the six points that Chicago scored, while the Bulls shot 2-for-10 from the field in overtime.
Chris Douglas-Roberts netted 13 -- 12 of which came in the fourth -- and Gerald Henderson had 11 points and six rebounds for the Bobcats (43-39), who could earn the sixth seed in the Eastern Conference playoffs if the Washington Wizards lose on Wednesday at Boston. Al Jefferson had 10 points and 18 rebounds.
D.J. Augustin netted 17, and Carlos Boozer and Joakim Noah added 14 points apiece, with 11 and 13 rebounds, respectively, for the Bulls (48-34), who are the No. 4 seed in the Eastern Conference after the loss. Jimmy Butler and Mike Dunleavy added 12 points apiece in defeat.