Both Eliza and Henrietta are described as being white, of slim build, with long, brown hair.
They moved to Scotland about seven years ago.
They are said to be part of a “close-knit” family, who do not understand what may have happened to the pair.
It is understood that Henrietta works in a branch of Costa Coffee in Aberdeen.
Police said the side of Victoria Bridge in the Torry area, where they were last seen, contained many commercial and industrial units and searches were ongoing there.
After they crossed the bridge the sisters turned right onto a footpath, next to the River Dee, and headed in the direction of Aberdeen Boat Club.
