Keith Broadbent, aged 61, of Kingsley Road, Harrogate, was reported missing by his wife at around 6pm on Tuesday.
He was last seen by his daughter on Sunday driving his car, a blue Fiat Punto, along Knaresborough Road, between 5pm and 6pm.
His car has since been found in the car park of Conyngham Hall in Knaresborough.
Yesterday officers were conducting extensive searches along the banks of the River Nidd and the area surrounding Conyngham Hall in an effort to trace Mr Broadbent.
He is described as white, about 6ft tall, with a medium build, blue eyes and dark brown hair.
When last seen, Mr Broadbent, was wearing jeans or chinos, a thick oatmeal-coloured jumper and brown shoes.
He also wears a wedding ring and a watch with a black strap. Officers are urging people to be on the lookout for Mr Broadbent and contact North Yorkshire Police if they see him.
Insp Steve Ratcliffe, of Harrogate police, said: “At the moment we are concentrating our search around the area in which Mr Broadbent’s car was found and I am urging anyone who thinks they may have seen him in and around that location over the past couple of days to get in touch.”
Anyone who can help is urged to contact police on 101.