David Dempsey has been missing from his home in the Dublin 8 area since around 2pm on Monday afternoon.
He is described as being 1.52m (5ft) tall, and weighs around 95kg (15 stone).
David usually wears a Manchester United soccer jersey and a baseball cap. He normally wears sunglasses or ordinary glasses.
Gardaí are asking anyone who may have information about David’s whereabouts to contact Kevin Street Garda Station on 01- 6669400, the Garda Confidential Telephone Line 1800-666-111 or any garda station.