The purpose of the current study was to investigate antecedents of job involvement of professional employees working in government work settings. In that effort, this study examined whether four key characteristics of professional employees’ jobs: variety, significance, autonomy, and feedback, as well as their perceptions regarding their agency’s mission, rewards system, and the extent of their participation in decision-making process determine the level of their job involvement. These linkages were examined with data collected through an organizational survey from 764 professional employees working in geographically distributed offices in a large state agency. The analysis indicated that more than half of the total variance in professional employees’ job involvement could be predicted reliably by perceptions regarding the characteristics of their jobs and agency’s reward system. The results also showed that perception of an attractive and worthwhile agency mission accentuated the positive effect of task significance on professional employees’ job involvement. Implications of these findings for managing professional employees in government agencies are discussed.