Twenty-five-year-old Theophanous started his career in the academy at Millwall before signing for AFC Wimbledon where he scored 28 goals in just thirty games for the Dons' reserve side which got the striker a move to Staines Town in the Conference (National League) South the following season.
He signed for Bromley during the 2012/13 season before moving back to Staines for 2013/14 where he finished the season with 26 league goals making him the top scorer in the Conference South.
He signed for Farnborough in October 2014, moving to St Albans City at the end of the season for an undisclosed fee, scoring 18 league goals in his first season and 20 league goals in the 2016/17 season for the Saints.
He moved to Chelmsford City in March 2017 to help the Essex club with their play-off push, scoring 9 goals in ten games.
In June 2017, Theophanous signed for ambitious Bostik League Premier side Billericay Town, scoring over 15 goals in the first half of the season before going out on loan to Kingstonian in January where he scored 3 goals in his first two matches.