The homer, Kemp's 12th of the season, broke a 3-3 tie with two outs in the bottom of the eighth. Kemp finished with three hits and scored four runs, while Brad Ausmus had two hits and two RBI for the Dodgers, who scored just twice in the previous two games against the Astros.
Ramon Troncoso (4-0) got the win in relief. Dodgers' starter Hiroki Kuroda went five innings, allowing three runs on seven hits with two walks and one strikeout.
Closer Jonathan Broxton earned his 22nd save.
Houston scored three runs in the third on Carlos Lee's RBI single and Geoff Blum's two-run homer. Michael Bourn had two of the seven hits for the Astros, who have won five of their last seven games at Dodger Stadium.
The losing pitcher was closer LaTroy Hawkins (1-4).
Houston starter Russ Ortiz surrendered two runs and five his in six innings with two walks and four strikeouts.