Michael Young, who was 3-for-3 with two walks after missing two games with a stiff back, started the Rangers' six-run sixth with a single to right off Mariners reliever Mark Lowe.
That brought up Hamilton, who was hitless in his first three-at bats -- he hit into a double play then left four baserunners on in his next two at-bats. This time, he swung and missed weakly at a changeup, then choked up on the bat and drove a fastball over the left-field wall.
"That's the first time in my career I've choked up on the bat and just tried to put the barrel of the bat on the ball," Hamilton said. "Obviously, my other at-bats weren't great, but that at-bat felt good. Anytime you can make a play or hit a home run like that, it gets your confidence up. You breathe a sigh of relief. Everybody in the dugout was hugging me, and I was hugging them."
Hamilton was playing for the first time since April 26, but he was struggling even before going on the disabled list, hitting .242 with two home runs and 10 RBIs in his first 18 games on the season.
"I'm just so happy for him to come back and get a big hit like that," Andruw Jones said. "He was trying to get it done too badly. Right now, he's a little too anxious, but once he gets patient and start getting his pitches to hit, he's going to be the same player he was for us last season."
Hamilton's home run set off a six-run rally against the Mariners' bullpen and broke the game open for the Rangers. They needed a lift after struggling for five innings against Mariners starter Jason Vargas and then not scoring after having the bases loaded with one out in the sixth.
"We were all just glad to have Josh back in the lineup for us," said first baseman Chris Davis, who hit his ninth home run of the year and his fourth in the past eight games. "When he hit that ball, we were all like a bunch of little kids jumping up and down in the dugout. To have him do that was big for him and a big pickup for us."
Rangers rookie reliever Derek Holland, pitching in relief of starter Scott Feldman, retired all five batters he faced to earn his first Major League victory. He lowered his ERA to 1.74 in six relief appearances since coming to the big leagues. Four of those have come in relief of Feldman, a deliberate tag-team arrangement on the Rangers' part.
"My first victory," Holland said. "I don't know what to say, especially against the Mariners -- a good ballclub -- and Ken Griffey Jr., who I grew up watching. I'm speechless. I can't believe it. I'm still stunned."
Feldman allowed one run on four hits over 6 1/3 innings and now has a 2.74 ERA in four starts. He threw 109 pitches, his highest total in 29 Major League starts. He took a 1-0 lead into the seventh but came out after giving up a one-out single to Franklin Gutierrez, a stolen base and a game-tying double to Kenji Johjima.
"Stuff-wise, I didn't have as good of stuff as I've had," Feldman said. "I would have liked to have gotten through seven. I'd like to go deeper in the game. I'm working on that, working on my stamina and working to keep my pitch counts down."
Maybe, but since the night Feldman stepped into the rotation for Kris Benson on April 24 against the Orioles, the Rangers' pitching staff has a 3.52 ERA in 17 games. Their starters are 9-3 with a 3.42 ERA in that stretch.
"It's great to have Josh back in there, but the story tonight was pitching," Young said. "First Feldman and then Derek. Right now, pitching is leading the way, and we couldn't be happier."