Diogo Spencer, a Lisbon native, joined Benfica's academy as a boy and signed his first professional contract in 2020. Originally a midfielder, he was converted into a right-back and can also cover the opposite flank.

He won the UEFA Youth League with Benfica in 2021/22.

Spencer was registered in the senior squad with the number 82 for 2024/25 but made no first-team appearances during the season, playing instead for Benfica B in Liga Portugal 2 and for the club's under-23 side. He signed a contract extension in December 2024.

He has one cap for Portugal at under-20 level.