This research offers an insight into the effects of the organizational culture of domestic and multinational pharmaceutical companies of Pakistan, on the job satisfaction levels of employees working in them, through the mediating effects of perceived levels of interactional justice. By explaining the interactions between organizational culture, interactional justice and job satisfaction, the managers and owners of those organizations shall be able to modify and inculcate the requisite changes in their organizational cultures to enhance the output levels of their employees through increasing the job satisfaction levels. Through this research, it is empirically established that organizational culture is positively and significantly related to job satisfaction. Furthermore, it is also established that interactional justice also has a significant and positive mediation effect on the relationship between organizational culture and job satisfaction levels of the employees. Through analysis of data collected from a total of 396 employees working in 11 domestic and multinational companies operating in Pakistan, using convenience sampling technique, it is established that organizational culture, interactional justice and job satisfaction levels of multinational pharma companies are relatively better than domestic pharma companies. This difference is empirically attributed to better organizational cultures of multinational pharma companies in the research. Based on the analysis, it is recommended that organizational culture of a pharmaceutical company can be improved by adhering to written rules and procedures instead of relying on verbal instructions. Moreover, a culture which supports and encourages innovation and initiative shown by employees improves the organizational culture prevailing in the organization. Equitable pay scales and fair chances of upward mobility within the organizational hierarchy through timely promotions also result in better score of organizational culture, thus increasing the overall job satisfaction levels.