The teenager was an unused substitute in Saturday's 0-0 draw with Chattanooga Red Wolves SC.
The younger Beckham, who celebrated his 19th birthday with members of his family on Wednesday, is the second oldest of four Beckham children and has reportedly been training with Fort Lauderdale and Inter Miami in recent weeks. Romeo Beckham joins Harvey Neville, the son of Inter Miami manager Phil Neville, on the Fort Lauderdale roster.
The bio on Romeo Beckham's Instagram account says "Footballer for @fortlauderdalecf". Other entries on the account show him training with the team, with one having the caption "Follow your dreams." His mother, fashion designer Victoria Beckham, left a comment on the post saying, "We are so proud of you Romeo."
Fort Lauderdale is in fourth place in the third-tier League One standings.