The Democratic Party that has dominated Cook Islands politics for the last decade has lost its grip on power.
Preliminary results from Thursday's general election show the Cook Islands Party has taken 15 of the 24 seats.
The Democrats have eight seats and one is tied.
Postal votes are still to be counted, but Radio New Zealand International's correspondent says it is unlikely these can reverse the preliminary counts.
Cook Islands Party leader Henry Puna says discontent with the ruling Democratic Party was the foremost reason for its loss.
He says his government's priorities will include introducing high standards of governance, particularly regarding the use of public money.