It was the 14th league win for Cardiff, but Newbridge put up a brave show and led 17-12 at one point.
Cardiff tries came from forwards James Goode (2), Chris Purcell and James Malpas with a penalty try and other touchdowns from backs Leon Andrews, Richard Jones and Liam Roberts. Andrews converted one and replacement Chris Anderson goaled six.
Newbridge, with several new faces, scored tries by wing Mark Addis and forwards Leighton Davies, Tom Lampard and Stuart Coles with a conversions each by fly half Ross Watts and full back Ross Jones.
Tonight (Wed) Bedwas entertain Pontypridd (7.15pm) with the return at Sardis Road on Saturday.
Nearly 40 players were involved in the first Wales Under 18 training session of the season. WRU National Performance Manager Gethin Watts is excited at the potential shown by the group and expects the Regional Under 18 Championship to hone their skills even further.