Dewar served his apprenticeship as a ship's upholsterer before embarking on a full-time career as a professional footballer. A powerful centre half, he came to prominence in local football with Dumbarton Athletic before joining Dumbarton in September 1887, winning his two caps in the two subsequent years. His first cap came on 24 March 1888 in the British Home Championship match at the Solitude Ground, Belfast where he scored the opening goal in the 10–2 rout of Ireland. He also played in the 3–2 victory over England the following April. One of the people watching the England v. Scotland game in April 1889 was Tom Mitchell, the secretary of Blackburn Rovers. He was looking to strengthen his side by buying the best players from Scotland. Mitchell persuaded Dewar to join Blackburn; in doing so, he brought an end to his international career as at this time Scotland did not select men playing in England. Dewar became a fixture in the Blackburn team over the next few years, playing 174 league matches; he even turned out for the Football League against their Scottish counterparts. In the FA Cup final against Sheffield Wednesday at The Oval on 29 March1890, Rovers were the odds-on favourites to win in view both of their record of three victories in the previous six seasons and their superior league placing. Blackburn fielded a teamconsisting of nine England or Scotland internationals. Rovers lived up to expectations as they romped away with the Cup defeating their Yorkshire opponents 6–1 with goals by Billy Townley, Nat Walton, Jack Southworth and Joe Lofthouse. Blackburn reached the FA Cup Final again in 1891. On this occasion Notts County were their opponents. In the final, played at Kennington Oval on 21 March, Rovers put County under pressure from the beginning and in the 8th minute, centre-half Dewar scored from a Townley corner. Before the end of the first-half, Southworth and Townley had added further goals. Jimmy Oswald of Notts County scored a late consolation goal but Blackburn finished comfortable 3–1 winners and won the FA Cup for the fifth time in eight years. In June 1897 he moved to New Brighton Tower and was part of the team that won the Lancashire League championship. Although New Brighton Tower would now be playing in the Second Division of The Football League he decided to move on and joined Southern League champions Southampton, who had just moved to their new home at The Dell. At Southampton he only made four appearances in November/December 1898 replacing the injured Bob Petrie. Now in his thirties and with his best days behind him he retired from football in 1899 and returned to his native Scotland. Dewar died of cancer in a Birmingham hospital in 1915 aged 48.
