This study aimed to investigate the relationship between Managers' Formal Sources of Power (Legitimate, Reward, and Coercive) and Open-Book Management practices (OBM) (Sharing information, Training, Empowering, and Rewarding) on the workers in special centers and units at Mansoura University. The study employed a deductive approach, and a quantitative research method. A questionnaire was used to collect data from 794 workers (with 88.12% response rate). A Partial Least Square (Warp-PLS V.7) was applied to test the research hypotheses and show the causal relationships between study variables. research findings showed that there is a significant correlation between managers' formal sources of power and OBM practices, where legitimate and reward powers had significant positive correlations while coercive power had significant negative correlation with OBM practices in special centers and units at Mansoura University. Findings also revealed that managers' formal sources of power had a significant direct impact on OBM practices, where legitimate and reward powers had significant direct positive impacts while coercive power had a significant direct negative impact on OBM practices in special centers and units at Mansoura University. Finally, theoretical and practical implications were presented in addition to future research suggestions.