The 19-year-old started in his famous dad's midfield position for the reserve team of Inter Miami - the Major League Soccer side owned by Beckham - in a 2-2 draw at home with South Georgia Tormenta.
"Blessed to have made my pro debut tonight," Romeo wrote on Instagram.
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The teenager, who signed a contract with the club in early September, showed some good touches and created an early chance for his new team.
He also linked up well in the midfield with Harvey Neville, the son of Inter Miami head coach Phil Neville - who graduated from Manchester United's Class of '92 with Beckham senior.
Young Neville was making his 16th appearance for the Florida-based side after leaving Manchester United's academy to join his father in the United States.
Beckham was substituted after 79 minutes and said it was now "full focus on to the next match".
Both teenagers are set to be back in action against Greenville Triumph on 2 October.
Beckham senior created global headlines when he made a surprising switch to LA Galaxy from Spanish giants Real Madrid in 2007.
He won back-to-back MLS Cups in 2011 and 2012 and in 2019 had a statue built in his honour outside La Galaxy's stadium to celebrate his six years with the club.