McCollum scored 30 points and Lillard added 28 for the Trail Blazers, who won their ninth straight game.
The Warriors were going without two-time league MVP Stephen Curry, who missed the game after suffering a sprained ankle in Thursday's 110-107 win over San Antonio.
Kevin Durant poured in 40 points and Klay Thompson added 25 for the Warriors, who saw the end to a seven-game win streak.
The Blazers shot .494 from the field, including 16-for-39 (.410) from 3-point range, and won the rebound battle 46-33. Portland held a huge advantage in bench points, outscoring Golden State's reserves 47-16.
Lillard scored 15 points and McCollum 13 as Portland took a 61-52 advantage into the half. Durant had 22 points for Golden State.
The Warriors scored the first six points of the third quarter to close to within 61-58. They went ahead 77-73 on a 3-pointer and a long jumper by Durant midway through the quarter. A long 3-pointer by Durant made it 83-77 late in the quarter. The Blazers followed with a 10-0 spurt to carry an 87-83 edge into the final period.
Golden State was within 92-91 when Shabazz Napier converted a four-point play with 8:32 to go. That touched off a 12-2 spurt that gave Portland a 104-93 lead with 6:44 left. Thompson's 3 brought the Warriors to within 110-103 with 3:33 remaining.
McCollum sank a pair at the line to up Portland's advantage to 112-103 with 3:16 to play. The Warriors got no closer the rest of the way.
Portland made its first six shots from the field yet led only 15-12 to open the game. The Blazers hiked the lead to 33-24 late in the first quarter, then settled for a 33-27 advantage heading into the second quarter despite 14 points by Durant. Portland had a 16-3 edge on the boards in the opening period.
The Blazers scored the first eight points of the second quarter to go ahead 41-27. Golden State got to within 52-50 on a layup by Kevon Looney late in the quarter. Portland outscored the Blazers 9-2 from there to take a nine-point lead into intermission.
Besides Curry, Golden State was without forwards Andre Iguodala (wrist), Jordan Bell (ankle) and David West (arm) and guard Patrick McCaw (wrist).
--Field Level Media
Golden State | Portland | |
Kevin Durant 40 | Scoring | CJ McCollum 30 |
Kevin Durant 6 | Assists | Damian Lillard 8 |
Draymond Green 12 | Rebounds | Ed Davis 15 |
Kevin Durant 10 | Free Throws Made | Damian Lillard 8 |
Draymond Green 3 | Steals | Al-Farouq Aminu 1 |
Kevin Durant 2 | Blocks | Ed Davis 1 |
Team | Points | FG% | 3PM-3PA | FTM-FTA | Assists | Rebounds | Blocks | Steals | Turnovers |
Golden State | 108 | 48.7 | 12-28 | 20-24 | 20 | 33 | 3 | 5 | 12 |
Portland | 125 | 49.4 | 16-39 | 21-27 | 21 | 46 | 2 | 4 | 11 |