In today's competitive environment, continuous organizational change is the only way to grow and develop, and organizations must maintain their readiness for continuous change and show high flexibility. This study aims to investigate the role of intra-unit communication on the optimal variability of Caspian Pharmaceutical Company employees to organizational change. This research has been applied in terms of purpose and descriptive in terms of method. For this purpose, a questionnaire with 31 questions based on a seven-point Likert scale and a standard type was developed as the main data collection tool, the validity of which was confirmed by experts and its reliability by calculating Cronbach's alpha coefficient (respectively for the variable of internal communication). Unity and employees' reaction to change (0.852 and 0.774) were confirmed. For this purpose, 101 experts and employees of Caspian Pharmaceutical Company were randomly selected. Then, the collected data were analyzed by SPSS software using correlation methods (Pearson test) and path analysis. The results indicate that all 6 research hypotheses are confirmed. Thus, all components of intra-unit communication (communication-coordination-participation level) were reported to be effective in improving the two components of employee response (behavioral and emotional response).