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Arms of Caernarvonshire County Council granted by the College of Arms 21 July 1949.

The shield was composed of the combined arms of Owain Gwynedd and Llywelyn Ein Llyw Olaf (Llywelyn the Last). The three eagles were the arms of the former prince, buried in Bangor Cathedral in 1169. The three eagles were also emblazoned on the banners borne by the men of Caernarvonshire at the Battle of Agincourt, according to Michael Drayton. The four lions were the arms of Prince Llywelyn. They later became the arms of the Principality of Wales.

The crest was a castle, for the Conway, Criccieth and Caernarvon castles. Rising from the castle were the "Prince of Wales's feathers".

The supporters were sea-dragons: Welsh red dragons terminating in a fishtail. They were intended to signify the maritime situation and associations of the County. The base or "compartment" of rocks, depicted the coast and mountains of Caernarvonshire.

The motto "Cadernid Gwynedd", is a quotation from the Mabinogion.

(Source: Leaflet issued by County Council in 1950.)