Symbol stones were erected by the Picts and represent some of the best evidence for their presence in Caithness. The stones take various forms and shapes. Earlier examples are unworked slabs with symbols cut into one face. Some of the symbols are recognisable, such as fish; others are harder to interpret. Examples that can still be seen in the county are at Reay (NC952651) and Latheron Mains (ND198334), both built into modern walls.

Overlapping in date with the latest symbol stones are cross-slabs with symbols. These are carved in relief usually on carefully dressed stones. The use of the cross and Pictish symbols are associated with the conversion of the local population to Christianity. Fine examples are the stones from Ulbster and Skinnet, now in Thurso Museum.

Sculptured crosses which lack Pictish symbols have been found across the county. A fine example can be found built into the wall of a mausoleum in the graveyard at Old Reay (NC969648) and on the south side of the church at Lybster (ND248356). Although the crosses may be contemporary with Pictish stones some may be associated with the presence of Irish priests in the county.