The bus was traveling from Atlantic City, N.J., to New York Friday morning when passengers began to notice the bugs crawling about, CNN reported.
Passenger Dawn Alexander told ABC News the roaches were first spotted in the front of the bus.
"Then after a while, the panic got toward the back because we all started looking around and saw roaches crawling everywhere," she said.
"We thought it was one (roach). It turned out to be a whole house full of roaches," said another passenger.
"I sat down -- roaches started crawling up on our clothes, falling down from the ceiling. Everything," said another.
Greyhound spokeswoman Maureen Richmond told CNN the bus driver acted quickly when passengers alerted him to the problem.
"He immediately pulled the bus over and radioed our dispatch office for assistance," she said. "A second bus was immediately sent to continue the trip into New York. We have spoken with each passenger and provided full refunds."
Greyhound said it was investigating how the roaches got onto the bus.