Though victory was deserved with a 4-1 try-count, neither side played to expectations and it was not a good showpiece for the Division with both sides and the referee making far too many errors.
Fly half Chris Anderson, a former Neath player, opened the scoring with a penalty, but Neath hit back with a brace of tries by wing Richard Johnston, of which James Hook converted the second.
Two more Anderson penalties followed, but both he and Hook failed with attempts until Hook succeeded on the hour for a 15-9 lead. Neath skipper Gareth Morris then scored a try that Hook converted, but Cardiff replied with a dubious score from Chris Czekaj.
Another Hook penalty was followed by a corner try from Neath centre Andrew Bishop in the closing minutes.
The GB7s women's squad is currently training at Wales' Centre of Excellence where assistant coach Richie Pugh tells WRU TV's Graeme Gillespie some 'tough calls' will have to be made when it comes to finalising the 12 spots for Rio's Olympic Games.
Wales U20's Billy McBryde is looking forward to starting his first game against New Zealand this afternoon in the World Rugby U20 Championship where his side are looking to gain revenge from last week's pool defeat to the Kiwis.