The 13-year-old was cycling on the green trail near the Ranger Station at about 17:00 on Monday when he was approached by a man.
The suspect was 5ft 2in (1.57m) tall, of medium to large build, and had white hair but was balding. He was wearing a mustard coloured jacket, a red jumper, jeans and brown dress shoes.
Officers have appealed for information.
They are particularly keen to trace a dog walker who was in the area at the time. He is described as being in his 30s, and was walking a black and white bulldog-type dog.
Police are investigating after a teenage boy was indecently assaulted in Dundee's Templeton Woods.