Kendrys Morales hit a two-run homer and Michael Morse also connected for the Mariners. Seattle's winning string had been its longest ever in spring training.
Brewers starter Mike Fiers, vying to open the season with the club, went 3 1-3 innings and allowed two runs and three hits.
Two Mariners pitchers competing for spots in the starting rotation, Blake Beavan and Erasmo Ramirez, pitched three innings each. Beavan allowed three runs on six hits and Ramirez shut out the Brewers on one hit.