Both archaeological and isotopic data document dietary changes over the first five centuries of Western Pacific island settlement, a time period beginning with the Lapita expansion about 3000 years ago. This change is marked by a decrease in marine food intake and an increase in vegetal food intake occurring in the Late Lapita/immediately post-Lapita populations. The recent discovery of human burials at Talasiu (~2700-2600 cal. BP) in the Kingdom of Tonga opens new opportunities to assess this matter. We characterize the nature of the food items consumed by the Talasiu humans (n = 21) using collagen and apatite carbon and nitrogen stable isotope ratios. We conducted an intra-Pacific comparison to examine the use of marine resources and the contribution of horticultural products and to look at the homogeneity of dietary practices within the Tongan group. Isotope results indicate a mixed diet of terrestrial and marine resources including a differential contribution of more specific marine foods (e.g., non-reef fish/inshore fish and shellfish). The Talasiu dietary pattern appears closer to that of the early Lapita population of Teouma than to other Late Lapita populations suggesting a different pattern of dietary change at the eastern end of the Lapita distribution. The slower rate of change may be due to the small size of both the island and the population, and also the additional potential role of social or cultural factors.