The Under-21 team is effectively Swansea City's second-string side, but is limited to three outfield players and one goalkeeper over the age of 23 per game following the introduction of new regulations from the 2016–17 season.

Note: Flags indicate national team as defined under FIFA eligibility rules; some limited exceptions apply.

Following the Vetch Field's closure at the end of the 2004–05 season, Swansea City's second string have played at numerous temporary homes.

It fields an under-18s team in the South Division of the Professional Development League 1 and the FA Youth Cup.

Note: Flags indicate national team as defined under FIFA eligibility rules; some limited exceptions apply.