Alex Rios went 2-for-2 with two walks, a double and a run scored, while Michael Choice and Leonys Martin also drove in runs for the Rangers, who snapped a three-game skid.
Matt Harrison (1-0) spun 5 1/3 innings of scoreless ball, allowing only three hits and four walks.
"It's a huge team win for us. I tried to keep us in the game from the get-go," said Harrison. "I was able to make some pitches to get out of a couple jams early in the game."
Nolan Arenado extended his hitting streak to a franchise-record 28 games with a single in the third. Brandon Barnes and Michael McKenry both doubled for the Rockies, who entered the game with wins in six of their last seven.
"Ultimately, I'm just trying to help this team win. I think that's the reason why this streak went as long as it has," Arenado said. "I think if my mind was on the streak then I probably would've never gotten it."
Franklin Morales (3-2) was belted for five runs -- four earned -- on six hits with three walks across six-plus innings in the loss.
The Rangers opened the scoring in the second. Rios got aboard with one out on a double to left before Leonys Martin's RBI single to right brought him home.
Martin moved to second on a balk with Elvis Andrus batting. As Andrus struck out, Martin stole third and made it a 2-0 game after Colorado catcher McKenry's throw drifted into left field.
Troy Tulowitzki reached on a walk to lead off the sixth. Three batters later, Barnes pulled a double down the right-field line to put men on second and third with two outs, but Jordan Pacheco struck out to end the threat.
Fielder solidified the Rangers' lead after he crushed a shot to the second deck in right in the sixth.
McKenry hit a leadoff double to center in the seventh and moved to third on DJ LeMahieu's fly out. Charlie Blackmon flied out to right and Rios' laser of a throw home to catcher Robinson Chirinos barely beat a sliding McKenry at the plate to turn the double play and end the inning.
Chirinos doubled and reached third on Blackmon's fielding error in left. Shin- Soo Choo was hit by a pitch and Choice singled up the middle to score Chirinos. Adrian Beltre's fly out to left moved the runners up a base and Tommy Kahnle intentionally walked Fielder to load the bases. A wild pitch scored Choo to account for the final margin.
Joakim Soria took the mound in the ninth for the Rangers and retired the batters in order to secure the win.