This study aimed to assess the perceptions of the effectiveness of EPICOR-10 System on pharmaceutical inventory management in Tanzania taking the Medical Stores Department (MSD) in Dar es Salaam office as a case study. The study espoused qualitative and quantitative approaches under the case study design. Simple random and purposive designs were used to choose 76 samples while surveys and in-depth interviews were employed in data collection. Likert scale was used to measure respondents’ perceptions of the effectiveness of the system whereas five (5) point ordinal scales were used to rate the respondent's degree to which they agree or disagree with its effectiveness on pharmaceutical inventory management at MSD. The study revealed that the majority of the respondents 57.9% and 42.1% strongly agree and agree respectively that the system is effective in customer service delivery, while 48.7% and 31.6% of respondents strongly agree and agree respectively that the system helped in inventory tracking. Nevertheless, 36.8% and 46.1% of the respondents strongly agree and agree correspondingly that the system helps in cost reduction. Moreover, 48.7% and 35.5% of the respondents strongly agree and agree that the EPICOR-10 system enabled time-saving whereas 39.5% and 36.8% of the respondents also strongly agree and agree respectively that the system provides the accuracy of real-time information when managing pharmaceutical inventory issues. The study recommends that MSD should continue to utilize EPICOR-10 system effectively in inventory management practices while more considerations should be taken on improving the system in the areas of its flexibility when integrating with other activities of the organization. However, regular training programs to capacitate staff and other users on advanced features and functionalities of the system are essential for the continuous improvement of pharmaceutical inventory management in Tanzania and other health sectors in developing countries.