Drawing from an interactionist approach and feedback research, we examine the role of developmental feedback and proactive personality on newcomer task performance and helping behavior. Data were collected from 2 high-tech joint-ventures within the information technology and manufacturing industries located in Shanghai, China. Results based on 151 newcomer-manager dyads showed that supervisor developmental feedback (SDF) positively related to newcomer helping behavior and that SDF and coworker developmental feedback interactively predicted newcomer task performance. We also found differential moderating effects of proactive personality: SDF more strongly related to helping behavior when proactive personality was lower; conversely, coworker developmental feedback more strongly related to helping behavior when proactive personality was higher.