Forty species in twelve families of gammaridean Amphipoda are recorded from Upolu Island, Western Samoa. Three species are new to science, Rostrogitanopsis cuculla n.sp., Maeracoota tridentata n.sp. and Ischyrocerus apiensis n.sp. and are described and figured. Twenty-seven of the thirty-five species known from outside Samoa, are widespread. Eight species have limited extrinsic distributions, two being shared with Papua New Guinea, two with Fiji and Tonga, two with Kosrae (Micronesia) one with the Gambier archipelago and one with Moorea, Tonga and Fiji.