Phyllis Robin, 78, was last seen in the Aultgrishan area of Gairloch on Friday evening.
She is described as being 5ft 2in, with a slim build and short white and auburn hair.
The pensioner was last seen wearing night clothes - a pink top and spotted bottoms - and wellington boots.
Sergeant Kay MacRae, who is leading the search, said officers are growing increasingly concerned for Ms Robin’s welfare.
Police are appealing for anyone who has seen her, or who knows where she may be, to contact police on 101.