Randy Arozarena had three hits for the AL West-leading Mariners, who have won 10 of their last 13 games.
Baltimore, which was 1 for 9 with runners in scoring position, has lost three in a row for the first time since getting swept May 18-20 at Tampa Bay.
The Mariners tied it at 1 in the fifth on Ryan Bliss’ one-out sacrifice fly. Cole Young’s single ended Baltimore rookie Trey Gibson’s outing, and reliever Anthony Nunez walked Julio Rodríguez to load the bases. Naylor then lofted a fly just over the wall in right for his seventh homer of the season.
The Orioles closed within 5-2 in the seventh when reliever Matt Brash’s wild pitch reached the backstop and allowed Coby Mayo to score. Brash nearly walked Pete Alonso to force in another run two batters later, but Seattle challenged and Alonso was out on a called third strike. Colton Cowser grounded out to leave the bases loaded.
Baltimore also had a run removed following a review in the eighth a batter after Blaze Alexander’s RBI single made it 6-3. Pinch hitter Samuel Basallo made the second out on an apparent sacrifice fly to center, but video review found that Rodríguez threw out Alexander at second before a tagging Jackson Holliday scored.
Emerson Hancock (5-2) allowed a run in five innings and struck out three.
Andrés Muñoz worked a scoreless ninth for his 10th save in 15 chances.
Gibson (1-1), who was recalled earlier in the day from triple-A Norfolk to replace the injured Chris Bassitt on the roster, yielded three runs in 4 2/3 innings.
Seattle scratched shortstop Colt Emerson due to back tightness.
Seattle RHP Logan Gilbert (4-4, 3.79 ERA) faces Baltimore LHP Trevor Rogers (3-6, 6.29) on Tuesday.