This study had three objectives. First, we examined the relationship between careerist orientation and organizational citizenship behavior (OCB). Second, we investigated the mediating role of life satisfaction in the relationship between careerist orientation and OCB. Third, we examined whether expatriate employees (those sent abroad on full-time company assignment) differed from non-expatriate employees in the strength of the relationship between careerist orientation and OCB. The expatriate sample consisted of 232 U.S. expatriates working in United Kingdom and the non-expatriate sample consisted of 210 full-time employees working in various organizations in the United States. We used hierarchical regression analyses to test the hypotheses. Careerist orientation adversely affected OCB because of lower life satisfaction that the employees experienced. Expatriate employees with a high careerist orientation exhibited lower level of OCB than non-expatriates with a high careerist orientation.