A heat sink assembly having rotatable fins includes a housing, a first heat dissipating device, a rod, an elastic member and a lever. The housing includes a first sidewall having a first hole, a first sliding hole and a stop portion, and a second sidewall having a second hole and a second sliding hole. The first heat dissipating device is in the housing and has a third hole, a first protrusion sliding in the first sliding hole, and a second protrusion sliding in the second sliding hole. The rod passes through the first, second and third holes. The first heat dissipating device rotates between a first position and a second position with the rod of being a rotating center. A first end of the elastic member connects with the stop portion, and a second end thereof connects with the first protrusion. The lever moves with the second protrusion.