Pauley (4-8) allowed two runs and eight hits, struck out three and walked two.
Entering Monday night's start, the Mariners had scored only 18 runs this season in Pauley's first 13 starts. This time, his teammates provided him with six runs.
Pauley is winless in six home decisions, but is 4-2 on the road.
Brandon League pitched a perfect ninth for his fifth save in 11 chances.
Smoak, traded to the Mariners by the Rangers on July 9 in the deal that sent left-hander Cliff Lee to Texas, hit a towering three-run shot to left in the fifth off C.J. Wilson (14-8) that extended Seattle's lead to 6-1.
Smoak struggled in his initial go around with the Mariners and was sent to Triple-A Tacoma. He helped the Raniers win the Pacific Coast League championship with a .438 batting average in eight playoff games, then was recalled by the Mariners on Sept. 18.
Nelson Cruz's three-run homer in the seventh off Anthony Varvaro pulled the Rangers within 6-5.
But Seattle loaded the bases in the eighth and Franklin Gutierrez raced home from third on Pedro Strop's wild pitch to make it 7-5.
Vladimir Guerrero added his 29th homer for Texas, which had its three-game winning streak snapped.
Before the game, the Rangers raised the AL West championship flag after clinching their first division title since 1999 on Saturday in Oakland.
Texas manager Ron Washington had most of his regulars back in the lineup after resting five starters Sunday at Oakland.
Next on the Rangers' agenda: determine the makeup of their playoff roster.
Seattle took a 2-0 lead in the second on RBI doubles from Adam Moore and Greg Halman.
Guerrero's homer that glanced off the top of the left-field wall leading off the second made it 2-1, but Gutierrez's sacrifice fly in the third gave Seattle a 3-1 advantage.
Wilson allowed six runs and eight hits, struck out five and walked one in five innings while losing his third straight decision.
NOTES: The Mariners started five rookies. ... Seattle RHP David Aardsma, out since Sept. 19 with a left oblique strain, will play catch Tuesday in an effort to return to the bullpen before the end of the season. ... Halman's double was his first major league hit. ... Rangers OF Josh Hamilton took 25 swings off a tee, ran hard in the outfield, and shagged fly balls prior to the game. Hamilton has been out since Sept. 4 with two fractured ribs and muscle spasms in his right side, and he reported no discomfort after Monday's session. Manager Ron Washington said Hamilton must still go through a regular batting practice before he can play in a game. Hamilton missed his 23rd straight game. ... Texas RHP Frank Francisco, trying to come back from a muscle strain in his right side that sent him to the 15-day disabled list on Aug. 28, will throw in the bullpen on Tuesday. Francisco said his side feels fine after back-to-back throwing sessions in the outfield over the weekend, but Washington said Francisco is a long shot for the postseason roster, at least for the first round.