The drivers of both vehicles were rescued and doing well, police said.
Police were alerted shortly after 7.30 a.m (5.30am GMT) that the bridge had collapsed as a truck and a car were crossing over it. The car plunged into the river while the truck remained on the bridge in a nearly vertical position on a collapsed section that was raised at an angle out of the water.
A helicopter assisted in the rescue operation and pulled out the truck driver, police said. The driver of the car managed to get out of his vehicle by himself.
The nearly 500-foot-long bridge connects the west bank of the Gudbrandsdalslaagen River and the village of Tretten. The bridge opened in 2012.
The cause of the collapse wasn't immediately known.