The company says the policy will be implemented from May 25th.
Passengers travelling on the town link service in the midlands are being asked to wear face masks.
Slieve Bloom Coaches says from May 25th people without a mask won't be allowed to travel on the service.
The company says its for the safety of those on the bus and local communities.
The routes include Portlaoise to Tullamore via Mountmellick or Portarlington, Portlaoise to Borris-In-Ossory, Tullamore to Mullingar and Kilkenny to Portlaoise.