The Arms Park side established an early 10pts to nil lead but the home side battled back to lead 20pts to 10 midway through the second half. However with the introduction of influential fly half Nick Macleod, the Arms Park youngsters levelled with two tries scored in quick succession and Macleod added a late penalty and drop goal to secure both the win and title.
Prop Darren Ryan, wing Andrew Henry and centre Owain Ashman scored tries for the visitors while fly half Chris Anderson landed an early penalty and conversion before the dramatic intervention of Macleod.
Wing Elia Pellegrotti and scrum half Alun Lake replied with tries for the Brewery Field side with fullback Lloyd Warner adding a brace of conversions and penalties.
Llanelli U'21s maintained their pursuit of the runners up position with a 26pts to 21 success away to Ebbw Vale.
Number eight Aled Gravell was in superb form for the young Scarlets scoring two tries, one of which was described as the seasons best. Flanker Steve Thomas was also in fine form while wing Llyr Davies and centre Mark Sweeney crossed for further tries for the visitors.
Fly half Caerlon Thomas secured the victory with a hat trick of conversions. Centre Gareth Roberts and Gareth Green replied with tries for the home side and Ross Watts added a further try and three conversions.
Cardiff v Neath
U21 Cup Final
This Wednesday 24th April, 7.15pm at Bridgend RFC
The Half a Game initiative is currently sweeping across Wales and proving a major success. The scheme aims to give every young player at least half a game every weekend. WRU TV recently visited a festival in Narberth where clubs have fully embraced the initiative.
Both Bargoed and Swansea were seeking their first win of the Principality Premiership season this afternoon. It proved a fruitful day for the hosts - not only did they win, but Bargoed claimed a try bonus point.
Cardiff managed to keep their unbeaten record at home intact, but only just as Bridgend made them work extremely hard before the Blue and Blacks secured a hard fought Principality Premiership win at the BT Sport Arms Park last night.
Former Wales back row Andy Powell gives a guided tour of The Wern, home of Merthyr RFC, who are determined to prove a lot of people wrong and make their mark in their first season in the Principality Premiership.
Wales Sevens head coach Gareth Williams looks back on the Rio Sevens success where he helped GB win silver. He believes the successful campaign is a huge boost to his Welsh squad as they prepare for another World Series, as WRU TV's Graeme Gillespie discovers
British and Irish Lions head coach Warren Gatland will be heading back home to take on the All Blacks next year where for him, success for 2017 is all about going to New Zealand and winning a Test Series.
Last week all roads led to Eugene Cross Park where defending champions Ebbw Vale hosted this season's launch of the Principality Premiership. WRU TV's Graeme Gillespie was there to capture the thoughts of Damien Hudd, captain of Ebbw Vale, and WRU Head of Performance, Geraint John.
Llandovery made it three in a row when they defeated Aberavon in the final of the National Foster's 7s at BT Sport Cardiff Arms Park on Sunday. On another eventful day of sevens, Newport claimed the Plate and the Dragons won the women's crown
Last week saw Cardiff welcome players from around the world for the 21st Golden Oldies Festival. The tournament features players over 35 years of age, and this year's event saw a select few represent the WRU in a 'friendly' against the Wooden Spoon.
Wales Under 18 captain Callum Bradbury is delighted to have seen his side claim a narrow 18-17 victory against a strong SA Schools 'A' side to end the three-match Under 19 International Series in South Africa on a high note.