This study investigated the importance of expectancy-based job cognitions and job affect (the affective component of job satisfaction) in helping to account for “organizational citizenship behaviors” (OCBs; Organ, 1988). Data pertaining to the expectancy-based job cognitions (i.e., expectancies, instrumentalities, valences), job affect, and OCB performance of 65 state finance agency employees were examined. We anticipated that the effect of expectancy-based job cognitions on OCB would be partially mediated by affect-based job satisfaction. This expectation was confirmed in that, after controlling for negative and positive affectivity, generalized instrumentality beliefs were found to affect OCB-altruism directly, as well as indirectly through the influence of affect-based job satisfaction.