Background: Reporting weekly diseases data from regions to Ministry of Health and Social Welfare is one of method which is used to submit weekly diseases information from regions to the Ministry according to number of weeks in a year from 1st to 52th week. This method is a paper based, that enables diseases information to be available at the national level on time to allow for quick and important public health action. This is an evaluation study designed to assess factors which tended to influence weekly diseases data from regions to Ministry of Health and Social Welfare, to determine technical challenges and determine measures to improving the reporting design. Methodology: The quantitative study design was conducted in Tanzania mainland which consist all regions. A primary data type was collected through structured closed questionnaire which was administered to a total of 25 respondents’ samples size that was 100% countrywide, since each region was represented by single reporter. Data was processed and analyzed by using Microsoft Excel 2010. Results: Findings showed that there was higher understanding of factors which influenced reporting. Findings indicate that 100% of the participants were Health officers, 68% were regional IDSR focal person who understood well the system of reporting weekly disease data. The evaluation also revealed technical challenges associated with reporting; whereas 88% of participants acknowledged to have incurred cost during reporting, 71% viewed that approving weekly diseases data contributed to untimely reporting. Finally, there were measures identified for improving reporting; these include feedback report, supportive supervision and availability of IDSR guidelines. Conclusions: The evaluation concludes that, the ineffectiveness of reporting weekly diseases data was due to several reasons which include weekly reporter having many responsibilities, approving and signing weekly diseases by RMO before submission, costs of reporting incurred by reporters and weak or no supportive supervision and feedback.. So the evaluation recommends that government through its ministry must take responsibilities of making sure that reporting forms are available. The Ministry and its development partners should take responsibilities to elevating the costs incurred by IDSR focal person