Born in Islington, London, Comley joined Queens Park Rangers Academy at the age of nine, where he progressed through the age groups to eventually make his first-team debut in 2015. He made his club and Premier League debut on 24 May 2015 as an 80th-minute substitute for Karl Henry during QPR's 5–1 defeat at Leicester City on the final day of the season. After facing Carlisle United in the League Cup first round on 25 August 2015, Comley made a loan move to the League Two club on 21 January 2016 in an initial month-long deal. He made his United debut ten days later, starting in their 3–0 home defeat by Everton in the fourth round of the FA Cup. In just his third appearance for the club, Comley was sent off for a second bookable offence during Carlisle's 1–0 league defeat to Newport County on 13 February. His loan was extended until the end of the season in March 2016. He went on to make 13 appearances for the Cumbrians. On 31 August 2016, Comley signed for League Two side Grimsby Town on loan until January 2017. He made his debut on 3 September during Grimsby's 2–2 draw at Notts County. He made 22 appearances for Grimsby in all competitions before he returned to QPR in January. He made one appearance for his parent club, before rejoining Grimsby on loan until the end of the season. He made a further 13 league appearances for the club. On 31 August 2017, Comley joined League Two club Colchester United on loan until January 2018. He made his Colchester debut on 9 September in their 3–1 win against Crawley Town. At the completion of his loan, he had made 23 first-team appearances for the U's.
Colchester United
signed their former loanee Comley on a permanent basis on 17 January 2018 for an undisclosed fee. He joined on a -year contract. He made his second debut for the club on 27 January 2018 as a substitute for Courtney Senior in Colchester's 2–2 draw at Port Vale. He scored his first professional goal on 10 March in a 1–1 draw at Mansfield Town. On 28 April 2020 Colchester confirmed that Comley would be released at the end his contract in June 2020.
Bolton Wanderers
On 21 July 2020, Comley joined Bolton Wanderers on a two-year deal.
Brandon has an older brother James who is also a footballer. He played alongside James on his international debut against El Salvador in September 2018.
