Robert Trueman, aged 46, left the Edlington area at around 7.30am on Friday, July 28, telling his partner he was leaving for work.
He was reported missing on Thursday, July 31.
PC Chris Hovelle, of South Yorkshire Police, said: “We believe Robert may have travelled to Blackpool for work and although it’s not usual for him to work away for weeks at a time, it is unusual for him not to contact his family and friends during that time.
“We are unsure as to what Robert was wearing when he left, however he usually wears long jumpers.
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“Due to the length of time no one has seen or heard from Robert, we are becoming extremely concerned for his welfare and I’d like to ask anyone who has seen or spoken to him since he left for work that morning to please contact us.
“I’d also like to appeal to Robert directly to get in touch with us. Robert, your family are worried about you and are keen to know you’re safe and well, please if you read this, get in touch with us or them.”
He is described of a medium height and build, unshaven, with dark grey hair.
He also has a red devil tattoo on his arm.
Anyone with information should call South Yorkshire Police on 101.