Watford born centre forward Harry Smith began his long amateur career with Southern League Watford in 1908 just before leaving the 3rd Dragoon Guards, with whom he had served in the second Boer War, having reached South Africa eleven days before it ended, aged 19. He made his debut against Brighton & Hove Albion in a 3-0 home win in April 1908. On his second appearance, while on army leave, he scored a Southern League hat-trick against Crystal Palace, who were beaten 4-1 on the last day of the 1907-08 season.
When he suffered a broken leg at Southampton in November 1908, the opposition collected £14 for him and the Hertfordshire FA sanctioned a weekly allowance until he was fit to resume his employment. John Goodall brought him back from Southampton two weeks after the match. He scored 4 goals in 14 matches that season, the most he played for the Watford first team in any individual season. In total he scored 15 goals in 35 Southern League appearances, playing his final first team game in April 1913. He continued to play for Watford Reserves and played 41 times for the first team in wartime competition during the First World War, scoring 23 goals. He continued as a player on the club’s books until the close season of 1922.
He also represented Hertfordshire and played for Watford Orient in 1912-13.