The authors examine the moderating effect of occupational commitment on job stress when employees perceive employer's violations of psychological contracts. Data gathered from 364 nurses show a positive association between perceived breaches of psychological contracts and job stress. The data also indicate that this association intensifies as level of affective occupational commitment increases, suggesting an exacerbating effect of affective commitment. However, no moderating effect was observed for continuance occupational commitment. Research and managerial implications are discussed.