The win was the eighth in a row for the Chargers (10-3), who lead the AFC West by two games with three to play.
Dallas (8-5) fell a game behind NFC East leader Philadelphia, a 45-38 winner over the New York Giants.
Rivers connected on 21-of-32 passes for 272 yards. His 14-yard pass to Antonio Gates with 10:56 to play put the Chargers ahead 17-10 and 9 minutes later Kaeding made it 20-10 .
LaDainian Tomlinson ran 1 yard for a Chargers' score in the first quarter and Kaeding drilled another field goal in the second, this one from 29 yards.
Tony Romo threw scoring passes of 6 yards to Miles Austin and 9 yards to Patrick Crayton, the latter with 2 seconds left in the game, and Nick Folk kicked a 31-yard field goal for Dallas.
Romo was 19-of-30 passing for 249 yards.
The outcome continued a trend in the month of December for the two teams, and their quarterbacks. Rivers and the Chargers are 16-0 in December since 2005. Romo has a 5-10 record in December and Dallas has lost five of its last six December games.