This paper explores the Jerusalem Conference described in Paul’s Letter to the Galatians, 2.1-10. The Conference convened to debate the position of Gentile believers within the Jesus movement. At this time the Jesus movement was still a sect within Judaism. Admission of Gentiles posed a threat to Jewish identity because Jewish and Gentile interaction was limited by Jewish religious practices and observances. Including Gentile believers within the early church communities would involve orthodox Jewish believers in unorthodox contact with Gentiles and would demand that Jews share the covenant of salvation with the uncircumcised – a covenant which had previously been the exclusive privilege of Judaism. This investigation utilises modern socio-psychological research into group processes and behaviour. In particular, the threat to Jewish identity by admitting Gentiles into the early Jesus movement has been explored in the context of the Social Identity and Self-categorization Theories. Evidence from the literature of the time demonstrates that classical inter-group bias/conflict existed between Jewish and Gentile groupings with both groups exhibiting ethnocentricity with respect to their own norms and derogatory stereotyping of the out-group. The decision of the Conference was that Gentiles could be admitted to the early church without circumcision but it also included provision for separate missions to the Jewish and Gentile believers. This paper argues that some separation within the Jesus movement was needed so as to preserve the social identity of those Jewish believers who experienced threat to their identity by the admission of, and consequent unorthodox contact with, Gentiles.