The robbery was reported at about 11:47 a.m. Police said in a release that the man entered the credit union with a handgun and then fled on foot with an undisclosed amount of money.
He was last seen traveling south on Clyde Park Avenue from 36th, according to a release.
The suspect is described by police as a black male, 5 feet 4 inches tall wearing a red scarf, black hooded sweatshirt, black jeans and gloves. He was also carrying a drawstring knapsack, police said.
No customers were inside the building at the time of the robbery, police said. No injuries were reported.
Anyone with information on this incident is asked to call Wyoming Police at 616-530-7300 or Silent Observer at 616-774-2345.