This paper proposes that role stressors decrease helping behavior by undermining employees' normative commitment from a cognitive dissonance perspective and social exchange theory. We also propose two competitive assumptions of the moderating effect of perceived organizational support (POS). In this paper, we first examine these hypotheses in Study 1 and then verify the cognitive dissonance perspective in Study 2. In Study 1, we collected data from 350 employees of two enterprises in China. The results indicated that role stressors had a negative link with helping behavior via the mediating role of normative commitment. The results also showed that POS strengthened the negative relationship between role stressors and normative commitment. In Study 2, we invited 104 employees to participate in a scenario experiment. The results found that role stressors had an impact on normative commitment via dissonance. Our studies verified the combination of cognitive dissonance perspective and social exchange theory to explain the impact of role stressors on helping behavior.