PurposeThe support of host country nationals (HCNs) is a key determinant of expatriate adjustment and performance. The purpose of this paper is to explore underlying motivations for their support to expatriates. Previous research has shown that HCNs with pro-social motivation are more likely to help expatriates. Drawing upon motivated information processing in groups (MIP-G) theory, the authors test whether epistemic motivation moderates the observed relationship between pro-social motivation and HCNs’ support toward expatriates.Design/methodology/approachThe authors ran two correlational studies (N = 267) in the USA (Study 1) and South Korea (Study 2). Across two studies, epistemic motivation and social motivation were measured using their multiple proxies validated in previous research. The authors also measured HCNs’ willingness to offer role information and social support to a hypothetical expatriate worker.FindingsResults lend support to our hypotheses that pro-social HCNs are more willing than pro-self HCNs to provide role information and social support to the expatriates, but this occurs only when they have high rather than low epistemic motivation.Originality/valueThe current paper contributes the literature on HCNs helping expatriates by qualifying the prior results that a pro-social motivation (e.g. agreeableness and collectivism) increases the willingness of HCNs to help expatriates. As hypothesized, this study found that that case is only true when HCNs have high, rather than low, epistemic motivation. Also, previous research on MIP-G theory has mainly focused on the performance of small groups (e.g. negotiation, creativity and decision-making). To the best of the authors’ knowledge, this research is the first attempt to test MIP-G theory in the context of HCNs helping expatriates.