Building on Kahn's (1990) ethnographic work, a field study in a U.S. Midwestern insurance company explored the determinants and mediating effects of three psychological conditions — meaningfulness, safety and availability — on employees' engagement in their work. Results from the revised theoretical framework revealed that all three psychological conditions exhibited significant positive relations with engagement. Meaningfulness displayed the strongest relation. Job enrichment and work role fit were positively linked to psychological meaningfulness. Rewarding co-worker and supportive supervisor relations were positively associated with psychological safety, whereas adherence to co-worker norms and self-consciousness were negatively associated. Psychological availability was positively related to resources available and negatively related to participation in outside activities. Finally, the relations of job enrichment and work role fit with engagement were both fully mediated by the psychological condition of meaningfulness. The association between adherence to co-worker norms and engagement was partially mediated by psychological safety. Theoretical and practical implications related to psychological engagement at work are discussed.