The last confirmed sighting of 54-year-old William Mulvihill of Ozanam Villas, Ballybunion was on August 21st, in the area of the Kielduff roundabout.
Up to thirty members of the Civil Defence are assisting Gardaí in today’s search.
Drone technology is being utilised and the dog unit are joined by locals and members of Mr Mulvihill’s family.
Today’s search is to concentrate on the Abbeydorney to Stack’s Mountain region.
William Mulvihill is described as being 5′ 3′ in height, bald, and with a moustache, and was last seen wearing a brown jacket, blue shirt, and blue jeans.
Gardaí in Listowel are appealing to landowners and farmers to check their properties for any sign of Mr Mulvihill.