Southwood is currently on loan to Cheltenham from parent club Reading. Born in England, he plays for the Northern Ireland national team, who he qualified for through a grandmother. In May 2018, Reading announced that they had offered a new contract to Luke Southwood, keeping him at the club until summer 2023. In August 2017, Southwood joined Bath City on a six-month loan deal, which was extended until the end of the season on 3 January 2018. He was awarded player of the season after an outstanding year. In December 2018, he joined Eastleigh on an initial one-month loan deal, which was later extended until the end of the season. Eastleigh made it to the semi-finals of the National League play-offs with Southwood playing a key part in that success, winning player of the month in April. In August 2019, Southwood joined Hamilton Academical on loan until January 2020. Southwood signed a new contract with Reading until the summer of 2021, and then returned to Hamilton Academical on loan until the end of the season. In July 2022, Southwood joined Cheltenham Town on a season-long loan deal.