Several localities in the Vanuatu archipelago (South-West Pacific) are inhabited by communities with Polynesian linguistic and cultural features. Defined as “Polynesian Outliers”, their formation is interpreted as a result of settlement by peoples from Polynesia during the last millennium. However, bio-anthropological studies undertaken on present-day populations, as well as archaeological individuals, have only identified small proportions of biological components related to Polynesian populations. The origins, timing and modalities which have contributed to and resulted in the arrival of Polynesians into the Vanuatu archipelago thus remain to be defined. To address some of these outstanding issues, we propose an interdisciplinary approach, combining the latest bio-anthropological and archaeological evidence from the Polynesian Outlier of West Futuna (South Vanuatu). We combined results from phenotypic and palaeogenetic analyses on 15 individuals from two distinct periods (1100 BP and 300 BP) to provide a diachronic view of population relatedness on the island. Archaeological contextualization (individuals buried in marge or with the community) as well as biological characterization (age, sex, health) enabled us to demonstrate that females with Polynesian components were buried in close proximity to individuals of local pre-existing origin, suggesting the integration of exogenous females into the local society. Our findings, interpreted along with oral records, suggest several admixture events between Polynesian newcomers and pre-existing populations through exogamy practice during the last millennium. Our results do not support a scenario of complete population replacement by Polynesian individuals in the history of West Futuna, but rather point to social processes having a major role in the acquisition of Polynesian cultural features during the formation of this Polynesian Outlier community.