Beltre finished with three hits and two RBIs, helping the Rangers avoid a three-game series sweep. Mitch Moreland and Elvis Andrus each drove in a run.
With Texas trailing 3-1, Beltre led off the seventh with a drive to center against Hisashi Iwakuma (7-4). A.J. Pierzynski then singled and Lance Berkman walked before Moreland bounced a tying single up the middle against Charlie Furbush.
Andrus came up with a go-ahead sacrifice fly and Ian Kinsler capped the big inning with an RBI single.
Josh Lindblom (1-2) recorded the final two outs of the seventh to pick up his first win since Aug. 31, 2012.
Raul Ibanez homered for the Mariners, belting a tiebreaking two-run shot in the seventh. It was his 12th homer in his last 28 games, lifting the total for the 41-year-old slugger to 21 for the year.
Iwakuma, who came in leading the AL in ERA, allowed four runs and five hits in six innings. The Japanese right-hander is 0-3 with a 5.54 ERA in his last four starts.
Ibanez went 4 for 5 with three RBIs and Kyle Seager added three hits for the Mariners, who were trying for their first series sweep at Texas since 2002.