The accident happened at 9 Mile/M-36 just north of Washtenaw County.
A source said that the fire department was at the scene of an accident when a vehicle struck him. Gentry was transported to a nearby hospital.
He is reportedly in stable condition.
Police are working to clear the scene. The freeway on the northbound side was reopened just before 6 p.m.
Gentry, a longtime member of the department, has been the chief for two weeks.
Stay with FOX 2 for more information as it becomes available.