Public health surveillance systems are critical for monitoring infectious diseases in Tanzania. However, their effectiveness can be enhanced through methodological improvements. A mixed-method approach was employed, combining quantitative data analysis with qualitative interviews to assess the performance of surveillance systems. A multivariate logistic regression model was used to estimate the probability of disease outbreak notifications (OR = 1.25; CI: 0.98-1.61). The quasi-experimental design revealed a significant improvement in notification rates for certain diseases, with a 15% reduction in false negatives. This study provides evidence of the effectiveness of methodological improvements in public health surveillance systems and offers recommendations for further enhancement. Public health authorities should prioritise training and resource allocation to enhance surveillance system performance and reduce operational errors.