Robert Campbell, 40, has been missing from his home in Glasgow's East End for almost a week.
His family say his disappearance is totally out of character.
He last spoke to his mum Mary, 64, on Wednesday, June 13, when he asked her to collect his daughter Maddison from school.
Electrician Robert, from Barmulloch, who also has a 15-year-old son Jordan, was to pick up Maddison later that night – but didn't turned up and hasn't been seen since.
He was last seen by his mother at her home in Balornock about 9.20am.
His brother Stephen, 36, said: "We have not heard anything from Robert and are desperate to know that he is safe and well. This is very out of character.
"We would urge him to get in touch or let the police know he is OK."
Stephen added: "Mum picked up Maddison last Wednesday and thought Robert would be coming to collect her later that night, but he didn't turn up.
"It just doesn't make any sense. We have had to tell Maddison that her dad is working away as we don't want to worry her.
"We just hope that Robert comes through the door before we have to tell her anything."
Mr Campbell is described as white, 5ft 8in, of heavy build, with cropped light-brown hair and blue eyes and is clean shaven.
He has a tattoo on his lower back of the name Jordan, and a tattoo on his right arm of the name Maddison.
He was last seen wearing a red T-shirt, dark trousers and white trainers.
It is unknown if he was driving a vehicle.
Police have been carrying out an extensive search of the local area, making door-to-door inquiries, checking CCTV and speaking to family and friends in an effort to trace him, but so far there have been no further sightings of Mr Campbell.
Chief Inspector Simon Midgely, of Baird Street Police Office, said: "Concern is growing for Mr Campbell's safety as his disappearance is completely out of character.
"I would ask that anyone who has seen Robert or knows of his whereabouts contact us.
"I would also ask, if he is able, that Mr Campbell himself contact police to assure us that he is OK."
Anyone with information should contact Baird Street Police Office on 0141 532 4100 or their local police office as a matter of urgency.