Harden (4-3) returned from the disabled list to scatter five hits and two walks to notch his first win since June 1. He recorded three strikeouts.
Harden had been suffering from a strained gluteus muscle.
Frank Francisco twirled a scoreless eighth and Neftali Feliz collected his 29th save with a 1-2-3 ninth as the Rangers evened their three-game series with the Angels at one win apiece.
Guerrero delivered a two-run homer in the fourth, providing all the offense for the first-place Rangers.
Newly acquired Dan Haren (7-10) pitched well in his second start since coming to the Angels in a trade from Arizona, showing few effects of being hit in the forearm by a line drive in his previous outing.
Haren tossed a complete game, allowing two runs on five hits and two walks while striking out six.