In the top of the first, Ryan Ludwick dumped a parachute into short center off lefty Randy Wolf with the bases loaded and one out, giving the Cardinals a quick 1-0 lead.
Shortstop Rafael Furcal led off the bottom of the first with a sharp opposite-field single off St. Louis ace right-hander Chris Carpenter -- and Kemp walloped Carpenter's first pitch to him just to the right of straightaway center for a two-run homer and a 2-1 lead.
The Dodgers went on to ride the momentum from that inning to a 5-3 win over the Cardinals and a 1-0 lead in the NLDS.
"Feels great," Kemp said of his homer. "First inning, got a little momentum in the first inning, and off a good pitcher, got up and gave Wolf a little confidence to go back out there after a rough inning and we went from there."
Actually, the up-the-middle Dodgers -- including Wolf -- had begun to make amends even before the top of that first had ended.
It could have been quick curtains for Wolf, who labored through 32 pitches in the inning.
But after loading the bases with none out with an intentional walk of Albert Pujols and falling behind 2-0 to Matt Holliday, Wolf fired three consecutive fastballs past Holliday to get him looking.
Following Ludwick's dunker, which skimmed Belliard's mitt, it was the second baseman's turn to atone.
Belliard speared a hot up-the-middle smash by Yadier Molina -- which was slightly deflected by Wolf -- and his quick feed to Furcal triggered an inning-ending double play.
"We played well defensively," Dodgers manager Joe Torre said. "Casey Blake made some plays, the play Belliard made in the inning to start the play.
Kemp's blow was also early validation for Torre's decision to bat him in the two-hole.
Although Kemp had been used there before, it's not a common lineup spot for him. He batted No. 2 only 13 times in the regular season. The Dodgers were 9-4 in those games.
"Matt came out there and set the tempo," right fielder Andre Ethier said. "They scored a run -- they could have scored more -- and [we] got them back on their heels right there in that situation."