Helton, was a .652 lifetime hitter against Bobby Jones, sent a 1-2 pitch over the wall in right for his 25th home run. Jones was activated from the disabled list before the game.
Coming off his worst outing of the season, Jennings (16-6) gave up two runs and seven hits, striking out seven without a walk.
The Rookie of the Year candidate allowed a solo home run by Ryan Klesko in the opening inning and five hits in the first three frames, but he settled down, retiring 14 of the last 17 hitters he faced for his sixth win in seven starts.
He needs one victory to tie the club record for most in a season, set by Kevin Ritz in 1996 and matched by Pedro Astacio in '99.
Todd Jones worked a hitless eighth and closer Jose Jimenez tossed a 1-2-3 ninth for his 35th save in 40 chances as the Rockies avoided their first 10-game losing streak since July 4-17, 2000.
Jones (7-8) was roughed up for five runs and seven hits over four innings in his first start since Aug. 16.