Gardaí wish to seek the public's assistance in tracing Martin Dalton, 29 years, from Fairhill in Cork.
He was reported missing on Friday and has not been seen since October 21.
Martin is described as being 6', broad build, blue eyes and brown hair.
He was last seen in the Shandon Street area.
Anyone with information should contact Anglesea Street Garda Station on (021) 452 2000.