Jesus Montero finished 3-for-4 with a solo home run and four RBI to lead Seattle over Kansas City, 6-1, in the finale of a four-game set.
Michael Saunders and Brendan Ryan drove in a run each for the Mariners, who took three of four in the series.
"It was definitely a good series offensively to get some big hits and have a lot of extra base hits," said Mariners third baseman Kyle Seager. "I felt like in this series it was really good for us to get a little confidence going forward."
Felix Hernandez (8-5) worked eight strong innings, scattering eight hits and one run while striking out three.
Eric Hosmer hit safely twice and Chris Getz knocked in the lone run for the Royals, who have dropped eight of 10 overall.
"He can locate multiple pitches," remarked Getz of Hernandez. "He's got above average stuff pretty much across the board. When you've got all those tools, that makes it pretty difficult as a hitter because you never get too comfortable."
Recalled from Triple-A Omaha, Will Smith (1-3) allowed four runs on eight hits in 6 1/3 innings for the loss.
Down 5-1 in the eighth, the Royals mounted one last charge, loading the bases with one out after Salvador Perez and Jarrod Dyson singled with an Alex Gordon walk. But Alcides Escobar fanned swinging and Billy Butler grounded out to short, and the Mariners tacked on their sixth and final run in the ninth.
Dustin Ackley led off with a single, Ichiro Suzuki added a base hit, Ackley moved to third on a fly out and came in when Montero lofted a fly to center.
Seattle jumped on top with a three-spot in the second as Montero led off with his ninth homer of the season and later in the frame Saunders singled home a run and Ryan followed with a sacrifice fly.
The clubs traded runs in the fifth with Montero singling home Suzuki in the top of the inning and Getz driving home Hosmer -- who doubled to start the frame -- in the bottom half.
It was a four-run margin for the visitors in the seventh after Casper Wells drew a walk against Louis Coleman and Montero followed with an RBI double.
Montero finished the series 10-for-17 with three doubles, five runs scored and eight RBI...His four RBI tied a career best, set last September 24 against Boston for the Yankees and on May 30 at Texas for Seattle...These clubs face each other one more time in 2012, at Seattle for a four-game set from July 26-29...Also on Thursday, the Royals signed veteran catcher Jason Kendall to a minor league contract.