Gareth Blundell, 36, went missing at around 3pm.
He is described as white, of large build and with short, dark hair and a beard.
Police have said he is believed to be heading in the direction of Blackhall Rocks and have asked anyone who may have information to call 999.
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Durham Constabulary said: Officers are becoming increasingly concerned for the 36-year-old who went missing from home in Blackhall at around 3pm today.
“Mr Blundell is described as white, of large build and with short, dark hair and a beard.
“He was last seen wearing a grey Nike tracksuit bottoms, blue Reebok trainers and a blue Chelsea tracksuit top and is believed to be heading in the direction of Blackhall Rocks.
“If you have any information that could help trace Mr Blundell, call 999.”