This study aimed to examine the impact of knowledgeable workers on water service delivery in Zanzibar with the specific case of Zanzibar Water Authority (ZAWA). A case study design involved both qualitative and quantitative approaches. A total of 80 ZAWA employees were involved as sample size in this study. Data was collected by using in depth interview and semi closed questionnaire. Content analysis was used to analyses qualitative data, whereas quantitative data were analyzed by using Statistical Package for Social science (SPSS) to get both descriptive and inferential data. Moreover, qualitative and quantitative data were presented by table and narrations respectively. The finding of this study revealed that knowledgeable workers have the great role to play to ensure quality and affordable water service delivery to the citizen. The study also revealed that ZAWA effort goes to proper managing in collaboration with organizational learning for better creation, sharing and application of different skill to ensure sustainability and retention of knowledgeable workers. The study recommended the need to identify quality staffs with required skills and professional based on organizational objectives for the better delivering of water service to the people. ZAWA should motivate the knowledgeable workers so as to retain and sustain them for the current and future needs of ZAWA.