Background: Social Health Insurance Scheme is a health scheme insurance which is provided by the governments to its employee. Tanzania introduced social health insurance by establishment of the National Health Insurance Fund (NHIF) in 1999 with the objective of improving the quality and availability of health services to Government employees (NHIF,2003). NHIF facilitates access of health care services to its beneficiaries through a network of accredited health facilities countrywide. This study evaluated NHIF service provision in accredited health facilities, challenges encountered and improvement measures. Methodology: The study was conducted in Dar es salaam, Temeke Municipal. Facility based multiple case studies of both quantitative and qualitative nature was carried to evaluate NHIF service provision in selected accredited health facilities. A total of 80 respondents from 10 selected accreditted health facilities participated in the study. The study population comprised of both male and female health workers aged 18 to 60 years with the education level from secondary to university and above, close to fifty percent (45%) had a working experience of more than ten years. Data was processed and analyzed by using Microsoft excel and Statistical Package for Social Sciences (SPSS) software. Results: Over half of the respondents (51.3%) agreed that NHIF objectives were achieved and there are several benefits gained by the beneficiaries and community from accredited health facilities. Besides, a number of challenges were reported to have been encountered by the accredited health facilities in the process of implementing the NHIF service provision. For example, 41.3% mentioned low Government health budget to the facilities as the main challenge and 36.3% mentioned lack of active monitoring mechanism to ensure appropriate and timely reimbursement of funds from NHIF. In addition, 20% recommended that stakeholders‟ involvement in decision making is one of the strategies to improve the NHIF service provision. Conclusion: From these findings, the following recommendation can be drawn; more effort is still needed to address the challenges encountered by accredited health facilities. These efforts include regural supportive supervisions to the facilities, training to health workers, timely distribution of working tools and timely claims reimbursement. However, measures to be taken to improve performance include; active monitoring mechanism of NHIF funds, reviewed NHIF quarterly reports, develop NHIF in charges at all facility levels, train NHIF coordinators, facilitate head of departments and increase health budget. The information contained in this evaluation is intended to create opportunities for multi-sectoral dialogue, to enhance collaborative planning efforts, and ultimately to facilitate partnerships that lead to increased health systems efficiencies and sustained health services.