Jack Musika, representing Coogee Beach Surf Life Saving Club, claimed the win in the under-14 male beach flags division.
A day earlier he had claimed silver in the under-14 beach sprints.
Musika said he was nervous ahead of his first race.
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READ NOW"There were top-level performers there and I just wanted to perform well," he said.
"I went over wanting to make the finals but I didn't expect to medal."
Musika said the competition was tight.
The judges were tough on anyone breaking at the start and with no second chances, there were plenty of disappointed athletes.
"I didn't really know how good everyone else was or where Id fit in with them," he said.
"But after the first race I was a lot calmer.
"I was really happy to win the medals."
Coogee Beach SLSC surf sports director Darren Spencer said the medals were a reward for effort.
"There's a lot of natural ability there but he's a good kid, quiet, modest and always competes hard," he said.
"He's at that age where a lot of the boys drop out so hopefully he can continue on because he's a good role model for our club."
Fellow club mate Wesley Muller, who competed in the Masters division, completed the two-man contingent from Coogee tackling the largest annual event of its kind in the world.
Muller claimed bronze in the 2km beach run for men aged 35-39.
In total more than 7000 competitors from 311 Australian surf life saving clubs flooded North Kirra Beach to compete in the event's centenary year.