Andino's bomb to left field off Charlie Furbush (4-2) saved a roller-coaster win for the O's, whose starter, Wei-Yin Chen, took a perfect game into the seventh inning but wound up not being involved in the final decision.
Chen struck out nine batters but served up a one-out home run to Casper Wells to spoil the gem.
The victory went to Darren O'Day (5-0), who recorded the final out of the eighth inning.
Jim Johnson picked up his 24th save.
Matt Wieters had a two-run single in the sixth for the Orioles, who ensured their first winning record at the All-Star break since 2005.
Seattle totaled five hits in the game, including a double by Michael Saunders that chased Chen from the game.