Duffus joined Everton in the summer of 2012 from Cheltenham Town. It came after Courtney, along with his younger brother, Tyrone impressed in the trial earlier that year. While at the academy, Duffus progressed through the ranks for the side and helped the side win the Gothia Cup and the league's U18 title. After being recalled from a loan spell at Bury, Duffus returned to the reserves and appeared in the first team as an unused substitute, in a 4–1 win over BSC Young Boys on 19 February 2015, in the Round of 32 of the UEFA Europa League. Despite suffering a knee injury following this, Duffus signed a two-year contract with the club at the end of the season. In the 2015–16 season, Duffus played a vital role for the reserve side when he regained his form at the end of the year and his performance resulted him being named the Premier League's Under-21 Player of the Month for March. The following season saw Duffus helped the side win the Premier League U23 title. After the 2016–17 season ended, which saw Tyrone released, Duffus signed a one-year contract extension with the club.
Bury (loan)
On 24 October 2014, Duffus joined League Two side Bury on loan until January. He made his debut a day later, starting the match and playing 59 minutes in a 1–1 draw with Southend United at Roots Hall. Duffus went on to make two appearances for the side before being recalled in November 2014.
Not long after signing a contract with Everton, on 18 July 2017, Duffus joined Oldham Athletic on an undisclosed fee, signing a two-year contract with the option of a third. Upon joining the club, he was given a number 21 shirt ahead of the new season. Duffus made his Oldham Athletic debut, coming on as a second-half substitute, in a 2–0 loss against Oxford United in the opening game of the season.
On 31 January 2019, Duffus joined Yeovil Town on a -year deal for an undisclosed fee.
International career
Duffus, and his brother Tyrone, are eligible to play for England, Republic of Ireland, due to his Irish mother, and Jamaica, due to his Jamaican father. In September 2016, Duffus was called by Republic of Ireland U21 for the first time and made his first appearance for Republic of Ireland U21s in a Euro qualifier against Slovenia. Duffus scored his first Republic of Ireland U21 goal in his third appearance for the national side, in a 3–1 loss against Serbia U21.
Personal life
Courtney's younger brother, Tyrone, plays for Cardiff. The pair also attended All Saints' Academy. Since late 2019, Duffus has been in a relationship with British tennis player Heather Watson.
