The king was being driven to an airport in Stockholm when the collision took place, palace spokeswoman Annika Sonnerberg said.
The car was badly damaged but King Carl Gustaf was uninjured and continued his journey in another car, local media said. There have been no reports of other injuries.
The role of king in Sweden is purely ceremonial.
Margaretha Thorgren, a press officer at the royal palace, told local media that King Carl Gustaf was “doing well” under the circumstances.
Photos published in local media showed damage to the front of the car, a dark blue Mercedes, with one air bag deployed.
King Carl Gustaf, 68, has now continued his journey to northern Sweden, where he is on a planned visit, palace officials say.
The king ascended the throne in 1973. He is best known abroad for presenting the annual Nobel Prizes.
Constitutional changes in 1974 deprived the king of all but ceremonial duties, such as opening parliament and representing Sweden at the diplomatic level.
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