Replacements: Cian Carroll, Cian Culleton, Sam Cooke, Billy Glynn, Emile van Wyck.
Replacements: Simon Bailie, Ali Coulson, Jonny Ogilby, Mark Marwood, Jack McMurty.
Rob Keogh's accurate place-kicking gave them a 13-3 buffer at the break, but they had to weather a storm from Malone who managed to go 20-18 ahead.
This was despite losing inspirational captain Glenn Moore to the sin-bin. The Belfast club put wingers Chris Leathem and Michael Barker through for second half tries.
Centre Josh Pentland also kicked well for the visitors, finishing with 10 points, but Malone had to settle for a losing bonus point as Glynn's score decided it in Blackrock's favour.
Blackrock retained the ball well early on given the wet and windy conditions, with second rows Des Dillon and Owen Cullen and recently returned flanker Gannon particularly prominent.
Malone opened the scoring with a penalty from Pentland before Keogh replied for the hosts. Both packs tried to dominate with ball in hand, attacking with vigour in the loose and profiting from solid set pieces.
The first bit of daylight between the sides was opened up when number 8 Langbroek broke through for the first try. Keogh added the extras and a subsequent penalty for a 13-3 advantage.
That was how it stayed up to half-time with Malone's attempts to respond being let down by some uncharacteristically poor passing and decision-making.
Jacques Benade's men came out strongly in the second period and put together some excellent phases of play which resulted in winger Leathem touching down. Pentland converted to make it 13-10.
Back came Blackrock and a spell of good pressure yielded a try for Connacht forward Gannon. Keogh was unable to land the conversion, leaving eight points between the sides.
Malone then upped the ante and they got the scoreboard moving again with a Pentland penalty and Barker swooped for a terrific try in the corner. Pentland topped that off with a tremendous conversion from the touchline which handed his side a sudden 20-18 buffer.
Malone kept plugging away while their skipper Moore was in the sin-bin, but Blackrock picked off a try that had a touch of good fortune about it.
The Dubliners pressed during a spell of attacking towards the clubhouse end. The ball came loose, squirting free from a ruck and alert replacement Glynn was on hand to score and move 'Rock ahead again.
That proved to be the final score of this entertaining encounter. Malone threw the kitchen sink at the 'Rock defence in the closing seven minutes. The frantic pace was not enough to prize open the hosts' rearguard and Blackrock held on in determined fashion.
Referee: Jonathan Peak (IRFU)