Despite the Dragons dominating the first half it was nine points from Patchell which put the Blues in front as the visitors failed to get points on the board.
The perfect start to the second half saw Tuilagi score the game's only try, and Wayne Evans add a conversion and a penalty to put his team in front, only for Patchell to slot his fourth penalty of the day.
And despite near-total possession of the ball in the latter stages, the Dragons found the Blues' defensive wall, as well as the sodden conditions which saw both sides finish caked in mud, too big an obstacle to overcome.
The visitors dominated the opening half in terms of both possession and territory but when it came to putting points on the board the Blues showed a much more clinical edge.
With the rain coming down, and the pitch very heavy underfoot, running rugby was at a premium, and with more than 70 percent possession and territory the Dragons would have expected to go in ahead at half-time.
Instead it was the accurate boot of Patchell that allowed the Blues to stretch into a lead, the young fly-half slotting three penalties in the space a quarter of an hour to put his team 9-0 up after 30 minutes.
The Dragons' frustration at Patchell's success was compounded by the difficulties their own place kicker Dan Evans was having in the conditions, missing two shots at goal as the Blues kept their visitors scoreless in the first 40 minutes.
Clearly Darren Edwards' team needed to score first in the second half, and they did just that when Dan Evans showed his goalkicking troubles weren't affecting the rest of the game with a perfectly-timed pass for Tuilagi.
When the powerful Samoan centre collected at full pace running at Harry Robinson, the diminutive winger was never going to stop him. Tuilagi then showed all his power to battle through a couple of desperate Blues players to dot the ball down. Wayne Evans, taking over the kicking duties converted to bring the visitors back to within two points.
And while Patchell had been nigh on faultless in the first half, he decided against a clearing kick in Blues territory taking the ball on instead and was penalised for holding on after getting isolated.
Wayne Evans again made no mistake to but the Dragons into the lead for the first time in the game and pile the pressure back on the home side with 20 minutes remaining.
However Patchell bounced back immediately, taking advantage of the Dragons going offside from the restart to slot his fourth penalty and put the Blues back in front.
The Dragons were clearly in the ascendancy however, and after five minutes of concerted pressure deep in Blues territory they had the chance to go back in front, only for Lewis Robling's drop goal effort to skew wide.
|Cardiff Blues Score Card|
|Newport Gwent Dragons Score Card|