Mills distributed seven assists and Duncan totaled 11 points with 13 rebounds as the Spurs claimed a seventh win in eight games.
Marco Belinelli added 14 points for San Antonio, which dominated the boards and drained 11-of-18 3-point attempts.
The Bucks hit just 37.5 percent shooting from the field in dropping a ninth straight.
2014: NFL Cheerleaders [PHOTOS]
UPI Sports Results for September 19, 2014