The recently recognized core construct of psychological capital or PsyCap (consisting of the positive psychological resources of efficacy, hope, optimism, and resilience) has been demonstrated to be related to various employee attitudinal, behavioral, and performance outcomes. However, to date, the impact of this positive core construct over time and on important employee well-being outcomes has not been tested. This study meets this need by analyzing the relationship between a broad cross-section of employees' (N = 280) level of PsyCap and two measures of psychological well-being over time. The results indicated that employees' PsyCap was related to both measures of well-being and, importantly, that PsyCap explained additional variance in these well-being measures over time. The limitations, needed future research, and practical implications conclude the article.