Blues North under 16s brought to an end the Ospreys' unbeaten run in the WRU Age Grade Championship and at the same time registered their first victory of the season.
After kicking off the campaign with defeats against the Dragons, Scarlets and Gogledd Cymru, the North edged out the Ospreys 19-17 in a real thriller at Pontypridd's Sardis Road.
Centre Callum Phillips, Joel Riggs and Josh Flye bagged tries for the hosts with Phillips and James Dixon adding a conversion apiece.
For the Ospreys, there were tries from Ryan Evans and Nicky Smith whilst Dan Thomas and Sam Davies added conversions and Thomas a penalty.
Team manager Nigel Way said; "we haven't been far away in our other games, but credit to the boys for sticking with it and coming away with a first win of the season."
Having started the season so brightly, defeat means the Ospreys slip further behind runaway leaders the Scarlets who defeated the Dragons 36-16 at the Recreation Ground, Tredegar.
With three victories under their belts already, the Scarlets bagged another bonus point in beating the Gwent region by four tries to two.
Jake Randall and Thomas Ball crossed for tries in the first half as the visitors swept into a 21-8 interval lead.
After that, it was a straightforward evening for the Scarlets as Sion Bennett and Dylan Morgan crossed for tries number three and four.
Jordan Williams, who went into the game with 55 points, kicked four penalties and two conversions as the Scarlets eased to another consummate victory.
Michael Adams and Dominic Franchi scored tries for the Dragons with Ethan Davies adding two penalties.
Cardiff Blues travel to Myreside on Friday to take on Edinburgh Rugby in a crucial Guinness PRO12 clash, and with Wales facing Scotland in the RBS 6 Nations at BT Murrayfield on Saturday, it promises to be a weekend of non-stop rugby action at the Scottish capital. Here are some useful advice to Cardiff Blues travelling supporters.
To celebrate the opening of the newly refurbished Guinness PRO12 Pack Bar, the world famous Irish brewer will be offering supporters free pints of the black stuff ahead of Saturday's clash with Ulster.
'TACKLE' - the first-ever joint community rugby initiative between the four professional teams in Wales has been launched (today Weds 19th October) bringing an inspiring new rugby education programme to young people in Communities First areas. Partners in the project were joined by Wales' star rugby internationals Sam Warburton (Cardiff Blues), Alun Wyn Jones (Ospreys), Gareth Davies (Scarlets) and Hallam Amos (Newport Gwent Dragons), for the launch at Aberdare Community School.
The Welsh Rugby Union, together with Pro Rugby Wales, has secured significantly improved insurance cover for all registered players, coaches and referees at each of its member clubs and regions at reduced costs -working with Aon, one of the world's largest insurance brokers and risk advisors.