Residents of a North Main Street address told police that shortly before 1 a.m. Wednesday a man broke in their door, demanded money and threatened them with a baseball bat.
The man and some accomplices made off with cash and other items, police said.
The department is investigating a rash of break-ins this month on the city's north side.
Anyone with information is urged to call the Jamestown Police Department at 483-7537.
Meanwhile, police also are investigating an incident in the parking lot of Wilson Farms on North Main Street, also Wednesday morning.
One person among several in a vehicle displayed a handgun and told a crowd in the parking lot, "We are from Buffalo and are taking over the city."