In the present study, we integrate Person-Organization (P-O) fit and Job Demands-Resources theories to argue that P-O fit (i.e., value congruence between person and organization) is a key resource that facilitates the accumulation and activation of situational job resources. We hypothesize that P-O fit strengthens the well-established positive relationship between job autonomy and job performance. Measures of objective P-O fit were obtained for 43 Norwegian naval cadets before embarking on a training mission onboard a sailing ship. During the mission, we measured daily self-reported autonomy as well as peer-rated task and contextual performance for 30 consecutive days. As predicted, the results of multilevel modeling analyses showed that the relationship between daily autonomy and (a) next- (but not same-) day task performance, and (b) next- (and same-) day contextual performance is stronger positive for individuals high (vs. low) in P-O fit. Moreover, effects of the daily autonomy – P-O fit interaction were noticeable on performance several days after. We discuss the theoretical and practical implications of these findings.