Cardiff made it a quickfire double over their near neighbours as they rattled up five tries without reply in the first-half to continue their good end to the season.
Having beaten Caerphilly 38-8 at the Arms Park eight days earlier, they matched that tally in the opening 40 minutes to pile on the points and consolidate their fourth place in the Welsh Premiership.
It was Wales full back Rhys Williams who started the early flourish as he ran in a solo try after 18 minutes. By the interval Dean Dewdney, Adam Jones, Don van Vuuren and Ryan Powell had followed suit.
It was not the kind of start that former Cardiff and Wales great Mark
Ring had been hoping for from his home side, especially as they have a major European final to come in two weeks time when they face Castres in the Parker Pen Shield final in Reading.
Things went from bad to worse shortly after the break when Wales utility back Iestyn Harris hoisted his match tally to 20 points with a try and a sixth conversion to further stretch the lead.
But far from throw in the towel, Caerphilly rallied and two more penalties from outside half Luke Richards gave them new hope. Then two tries in the space of four minutes, both converted by Richards, breathed new life into the final quarter.
Wing Ryan Howells crossed for the first of the home tries and then lock Darren Davies romped over moments after his opposite number Heino Senekal was sent to the sin-bin. But all that was left in the game were two more penalties from the two outside halves and Cardiff hung on for victory.
Caerphilly: Tries: R Howells, D Davies; Cons: L Richards 2; Pens: L Richards 6.
Cardiff: Tries: R Williams, D Dewdney, A Jones, D
van Vuuren, R Powell, I Harris; Cons: I Harris 6; Pens: I Harris 2.
On the day the Wales U20 squad for the Six Nations is revealed, WRU Head of Rugby Performance Geraint John discusses the priorities of the Wales U20 programme, and moves being undertaken to make it easier for Welsh Exiles to be part of the WRU pathway - and to help keep Welsh qualified players in Wales
It was a double celebration for Wales and Ospreys scrum-half Rhys Webb when he called at the home of Welsh rugby to help commemorate the first anniversary of Principality Stadium and his return to fitness this weekend ahead of the RBS 6 Nations.
Prior to their departure to Wellington for the next leg of the World Series, Wales trained with England and Ireland. WRU TV caught up with Owen Jenkins who revealed the 'buzzword' which is driving the Wales squad on.
Wales head coach Rob Howley explains his decision to change the captaincy of the national side with Ospreys second row Alun Wyn Jones taking over from Sam Warburton for the forthcoming RBS 6 Nations. Howley is hoping his decision will allow Warburton to rediscover his 'mojo'.
How do you follow a dancing hippopotamus - the Ospreys wheelchair rugby team has just the 'oneness' to do it say the BBC! For a decade the sight of a herd of hippos synchronised swimming around their own private blue lagoon, has lit up our television screens at regular intervals between favourite BBC One shows. But now the nation's most watched channel has relinquished its famous amphibious mammals in favour of a new show-reel which includes the Ospreys wheelchair rugby team.
Head coach Rowland Phillips and key front rower Carys Phillips look ahead to games against Spain and Ireland as Wales Women ramp up their preparations for the forthcoming Six Nations. The two warm-up games are a 'massive opportunity to refine the squad' according to the Welsh camp.
Martyn Phillips has discussed details of the newly published 'Strategy for Welsh Rugby' which puts in black and white terms the plans and direction of the governing body of the national sport in Wales for the next decade.
WRU chief executive Martyn Phillips has urged Welsh rugby fans to follow in the footsteps of their soccer counterparts at last summer's Euro Championship by backing their team to the hilt in the upcoming RBS 6 Nations campaign.
Chief executive Martyn Phillips has highlighted the plans for Wales to become a breeding ground for national and elite club rugby coaches, which are contained in the WRU's 10-year 'Strategy for Welsh Rugby'.
Andrew Coombs is enjoying his new role as Nelson forwards coach. The former Dragons and Wales lock has big ambitions to become a professional coach but feels it's important to learn the ropes in grassroots rugby and where better than his home club Nelson, with friends and family close to hand.
Students at Brynllywarch Hall School, near Newtown, have transformed their own lives, and are now having a positive impact on others through rugby. The sport has had a life-changing effect on the well-being of the students who are now delivering rugby sessions to local primary schools and playing for a new mixed ability side
Wales reached their first semi-final since 2013 in the opening round of this season's HSBC World Rugby Sevens Series in Dubai. WRU TV's Graeme Gillespie recaps on what proved to be an eventful tournament
Wales and Ospreys back row James King, who came through the North Wales age grade system, nominated North Wales Regional Community Rugby Manager Marc Roberts, in the WRU's 'Diolch' initiative where squad players thanked those who played a part in their rise to the top.
Beating Merthyr has boosted Carmarthen Quins hopes of reaching a top eight spot in the Principality Premiership. Quins captain Haydn Pugh is delighted with his team's progress and is determined that everyone from the Under 6s through to the senior team, enjoys the ride.