Robert Dolan, 50, from Clydebank was last seen around 4.30pm on Wednesday 28 December 2016 and was reported missing Tuesday 7 February 2017, say police.
He is described as white, 5ft 8ins in height and of slim build with short grey hair.
Inspector David Quinn, Clydebank Police Station, said: “It’s been nearly seven weeks now since Robert was last seen.
"We believe that he has travelled to the Blackpool area and staying there in bed and breakfast accommodation. Robert is a joiner to trade and he may also be working there.
“It is unlike Robert to disappear for this length of time without making contact with friends and family and as time passes, there is mounting concern for his well-being.
“I would ask anyone with information on Robert’s whereabouts, or indeed Robert himself, to contact the Enquiry Team at Dumbarton Police Office through 101 or to attend at a local police station.”