Hooker Ben Pereira had his radar tuned in, followed the ball and scored three tries for Alhambra-Union at Miller Park.
It was a lively game, with both teams prepared to chance their arm and spread the ball wide.
Alhambra-Union scored four tries in the first spell to lead 28-7 at the break and added four more in the second spell.
The key to the win was Alhambra-Union's dominance of the set pieces. It controlled the lineout, with flanker Matt Kissick making seven clean takes.
He was backed up by locks Jeremy McKee and James Willocks.
It was a Willocks take inside the Green Island 22m that led to the third try when midfield back Johnny Liaina used his speed to score after a ruck.
Flanker Graeme Cashmore helped the Alhambra-Union cause when he used his speed and strength to score tries on both sides of halftime.
The best players for Green Island were halfback Dean Moeahu, No 8 Junior Sala and utility forward Jackson Hemopo, who scored two second-half tries.
Alhambra-Union 52 (Ben Pereira 3, Graeme Cashmore 2, Matt Dalley, Johnny Liaina, Shaun Crockford tries; Peter Breen 6 con), Green Island 24 (SofeleTuiganala, Tala Moli, Jackson Hemopo 2 tries; Joe Bartlett 2 con). Halftime: Alhambra-Union 28-7.
