With the win, the Trail Blazers completed a sweep of the season series.
Wallace scored 23 points, hitting three three-pointers. The first two came on consecutive possessions in the third quarter and gave Portland the lead for good. The last was part of a crushing four-point play.
Anderson scored 18 points, draining four treys. He struck from the arc three times during the third quarter, when the Trail Blazers outscored the Sonics, 27-11.
"That's a team that doubles down a lot, and anytime you get a chance to take advantage of a 2-on-1 situation, you try to do that," Anderson said. "Me and Rasheed was doing that tonight. We just hit our shots."
Ruben Patterson also had a rare three-pointer as Portland made 8-of-16 shots from the arc. The Blazers swept the four-game set from the Sonics for the second time in the last four seasons.
"A lot of those threes we didn't take early on (in the shot clock)," said Portland Coach Maurice Cheeks. "Those threes are OK. We get ourselves in trouble when we come down with 18 seconds on the shot clock and we're firing three-point shots."
Portland limited Seattle to just 29 points in the second half, and held Ray Allen under 20 points for the first time since he joined the Sonics. Allen managed 14 points on just 6-of-20 shooting, including 0-of-6 from the arc.
"They kept a body on me at all times coming off screens," Allen said. "I didn't have any good looks. I felt like I just wanted it so bad that I started pressing to make shots. I've got to relax and let the game come to me, especially if teams are going to play me that way."
"I was trying to make Ray dribble a little more," Anderson said. "We tried to pressure them and take them out of their rhythm."
Seattle nearly tied the franchise mark for fewest points in a half. It scored 29 against Phoenix on Dec. 23, 1993.
Zach Randolph scored 17 points off the bench for the Blazers, who shot 51 percent (35-of-69) overall, and held a 41-27 rebounding advantage. Scottie Pippen had 13 boards and Dale Davis added nine.
Kevin Ollie had 15 points and 11 assists for Seattle, which shot just 41 percent (30-of-73), including 6-of-20 from the arc. Vladimir Radmanovic scored 12 of his 14 points on three-pointers.
Scoring forward Bonzi Wells was suspended for conduct detrimental to the team, but the Blazers still raced to a 30-18 lead after one period as Randolph scored eight points. Ollie had 10 points and six assists in the second period, when Seattle allowed just 12 points and rallied for a 48-42 halftime advantage.