Research on the relationship between perceived organizational support (POS) and affectiveorganizational commitment (AC) has primarily adopted a social exchange perspective. In thisstudy we considered complementary socio-emotional explanations of the POS–AC relation-ship. We focused on the mediating role of organization-based self-esteem (OBSE) and testedcompeting models of the POS–OBSE-AC relationship separately on data from two Koreanbanks that experienced different levels of downsizing following the 1997 Korean financialcrisis. We further extended the analysis by examining the extent to which the relationshipbetween POS and OBSE and AC, respectively, was affected by employees’ perceived sense ofjob insecurity in the two banks. The results showed that OBSE was a significant mediator of thePOS–AC relationship in both organizations. POS, however, also retained a strong independentdirect effect on commitment. Moreover, as expected, perceived job insecurity tended toattenuate the POS–OBSE relationship, but augmented the direct relationship between perceivedorganizational support and affective commitment