Geoffrey Bull was last seen at around 9am yesterday as he left his home address in the Woodlands area of Doncaster.
Officers are growing increasingly concerned for the 70-year-old’s welfare.
South Yorkshire Police, which is leading the search, said Mr Bull may have travelled to North Yorkshire and he is known to regularly visit the Pickering area.
He was last seen wearing a sky-blue hooded top, green trousers and brown boots.
Anyone who thinks they may have seen Mr Bull, or knows of his whereabouts, should call 101, ask for South Yorkshire Police and quote incident 541 of July 27 2017.