James Clegg, aged 37, was last seen at around 10.25am yesterday on Cavendish Street, Sheffield.
He is white, around 5ft 6ins tall and was last seen wearing grey jogging bottoms, a grey T-shirt with an orange motif and a green jacket. He was also carrying a green backpack.
South Yorkshire Police said: “We are asking anyone who knows where he is, or has seen him, to get in touch.”