The Pacific Islands AIDS Foundation is closing its Rarotonga headquarters and relocating to Suva due to funding constraints.
Its chief executive, Maire Bopp, says this is a direct result of the constraints placed on a small regional bodies.
One staff member will continue to do research in the Cook Islands, basing herself at the Rarotonga Red Cross building.
The rest of the staff have chosen not to relocate to Fiji.
The Pacific Islands Aids Foundation was set up in the Cook Islands in 2003, and a sister branch was opened in Fiji in 2009.
Cook Islands News reports a consultant hired by the New Zealand Aid Programme recommended the Suva relocation because it's cheaper to operate from there.