Flacco produced an 80-yard touchdown march in his only series, and the Ravens beat the San Francisco 49ers 23-3 Thursday night in a preseason opener.
It was the third time in three tries that Ravens coach John Harbaugh got the best of his brother, Jim Harbaugh, coach of the 49ers.
Baltimore previously defeated San Francisco on Thanksgiving 2011 and in the Super Bowl ending the 2012 season.
In this one, each team played its starting unit for one series before the backups took over.
After Colin Kaepernick moved the 49ers 66 yards for a field goal, Flacco made himself right at home in Kubiak's variation of the West Coast offense, going 4 for 5 for 52 yards.