In front of a home crowd of around 600 supporters, the Sharks overcame the Eels 18-14.
The win called for a celebration for the Sharks which managed to achieve the feat for the first time in 12 years of trying.
They have beaten every other team in the competition at various times, but the Eels have always escaped away with wins since they joined the competition.
“The surprise to all and the only club the Sharks have never beaten since joining the competition 12 years ago finally beating the Eels 18-14,” Cook Islands Rugby League competition co-ordinator Taua Benioni said.
“The Sharks never let the Eels have it their way from the start. With home advantage and everything going their way they deserved it. Eels had no answer or excuses.”
The Sharks defence was tested and especially in the last quarter when Jacque Henry, Teau Paerau and Messine Messine stood up and made repeated tackles to keep the Eels at bay.