AB did not play RCB's last game against Gujarat Lions due to a back injury while Mills was also ruled out.
The South African was seen practicing on Saturday, coming ahead of skipper Virat Kohli and Chris Gayle, who joined the team in the second-half of their training session.
Mills also rolled his arms at the nets for quite some time.
"He is fit and is available for selection," an RCB official told IANS on the sidelines of the team's practice session.
AB has so far played three matches scoring 137 runs, RCB's highest while Mills has three scalps to his name from four outings.