Based upon the Ancient Arms of Nova Scotia, granted by King Charles I in 1625, the background of the flag is an extended blue cross on a white background, a reversal of the colours found on the Cross of Saint Andrew, symbolizing Nova Scotia's links to Scotland. The flag is three-quarters has high as it is wide. In the centre of the flag is a Royal Lion set within a double red border on a yellow or gold background. This was the first flag to be flown in the Commonwealth outside of Great Britain.

The Ancient Arms of Nova Scotia were substituted by a less-impressive Arms in 1868 following Confederation. However, the new Arms were a poor substitute and the citizens tried for decades to have the original Arms reinstated. Finally, in 1921, the tricentennial of Nova Scotia's Royal Charter, historians and scholars met in Annapolis Royal to petition the government to have the Ancient Arms reinstated. In 1929, in response to the petition, King George V reinstated the Ancient Arms of Nova Scotia by Royal Warrant.