The positive core construct of psychological capital (or simply PsyCap), consisting of the psychological resources of hope, efficacy, resilience, and optimism, has recently been demonstrated to be open to human resource development (HRD) and performance management. The research stream on PsyCap has now grown to the point that a quantitative summary analysis of its impact on employee attitudes, behaviors, and especially performance is needed. The present meta‐analysis included 51 independent samples (representing a total of N = 12,567 employees) that met the inclusion criteria. The results indicated the expected significant positive relationships between PsyCap and desirable employee attitudes (job satisfaction, organizational commitment, psychological well‐being), desirable employee behaviors (citizenship), and multiple measures of performance (self, supervisor evaluations, and objective). There was also a significant negative relationship between PsyCap and undesirable employee attitudes (cynicism, turnover intentions, job stress, and anxiety) and undesirable employee behaviors (deviance). A sub‐analysis found no major differences between the types of performance measures used (i.e., between self, subjective, and objective). Finally, the analysis of moderators revealed the relationship between PsyCap and employee outcomes were strongest in studies conducted in the United States and in the service sector. These results provide a strong evidence‐based recommendation for the use of PsyCap in HRD and performance programs. Theoretical contributions, future research directions, and practical guidelines for HRD conclude the article. Gallup Polls in recent years suggest that Americans are pessimistic about incremental