Smith was moved to the 100-gun in 1665 and sent to the Mediterranean with a squadron of ships under his command. He returned to Britain and was appointed admiral of the blue squadron in the royal fleet, taking part in the Four Days' Battle in June 1666, under the overall command of George Monck, 1st Duke of Albemarle. Smith was knighted in June, and in July fought in the St. James's Day Battle, still as admiral of the blue, and commanding the rear squadron in the battle from . His squadron, the weakest of the English fleet, engaged the strongest Dutch squadron, under Cornelis Tromp. In doing so Smith prevented Tromp from coming to the assistance of Michiel de Ruyter, whose force was severely mauled by the van of the English fleet. After a period of fierce fighting Smith withdrew from the line, either by choice or by being forced out by the Dutch. Tromp followed, weakening the Dutch line. During the battle Tromp's flagship lost over a hundred men, and was nearly captured by Sir Edward Spragge, one of Smith's junior flag officers. The Dutch rear-admiral of Tromp's squadron was killed fighting Smith's force.