The 49ers scored 10 unanswered points in the quarter, which ended with the Vikings in San Francisco territory.
San Francisco got the second half started with a long kick return by Kyle Williams, setting up a 29-yard field goal by David Akers.
Following a three-and-out by the Vikings, the 49ers drove the field again, this time converting on a one-yard touchdown catch by tight end Vernon Davis.
Through three quarters, quarterback Alex Smith is 19/25 for 158 yards, one touchdown and no interceptions. Frank Gore has 10 rushes for 54 yards, and Davis leads all San Francisco receivers with four receptions for 46 yards and a score.
San Francisco's usually stout defense has been unable to get pressure on quarterback Christian Ponder, however, as he has yet to be sacked in the game.