Past research suggest that affect is an important component of job attitudes and an important predictor of some job behaviors (Weiss & Cropanzano, 1996; Brief & Weiss, 2002). This study extends previous research by investigating the relationships between positive and negative affectivity and employee helping coworker behavior, and examining the moderating roles of job type. Result from 191 employees of 15 firms partially supported our hypotheses and showed that positive affectivity was significantly positive related with helping coworker behavior. In addition, when the team orientation or internal-service orientation of job was high, the positive relationship between positive affectivity and helping coworker behavior became stronger.