Lillard, 22, led all rookies in scoring (18.2 ppg), assists (6.9 apg) and 3-pointers made (28) while helping lead Portland to a 9-4 record in December. His scoring average ranked 23rd in the NBA, and he placed 11th among league leaders in assists.
The 6-foot-3 point guard has now earned back-to-back Kia NBA Western Conference Rookie of the Month honors. He joins Brandon Roy (January, February and March 2007) as the only Trail Blazers in franchise history to win the award multiple times.
On Dec. 26, Lillard became the third-fastest Trail Blazer to reach 500 points in team history (27 games), trailing only Sidney Wicks (21 games) and Geoff Petrie (25 games).
Lillard is the only Trail Blazer to appear in every game so far this season. Portland selected Lillard with the sixth overall pick in the 2012 NBA Draft.
The Weber State product holds season averages of 18.4 points, 3.3 rebounds, a team-high 6.3 assists and 1.07 steals in 37.9 minutes.
Washington's Bradley Beal earned Kia NBA Eastern Conference Rookie of the Month honors.
Kia, a proud partner of the Portland Trail Blazers, will present Lillard with the Kia NBA Western Conference Rookie of the Month award later this month.