Inspite of efforts taken to overcome the cataract related blindness, Zanzibar as one among sub-Saharan countries are far behind the WHO target for good visual outcome following cataract services. Zanzibar claimed to have 41% good visual outcome out of 95% WHO target while the reasons are not much clear, hence a quest to assess the quality of cataract services provided in Zanzibar in terms of: competency of human resource available, availability of medical requirement and level of staff compliance with the standard operation guidelines. To address the evaluation objectives a case study design was applied to assess the quality of cataract services in Zanzibar involving both qualitative and quantitative techniques. The evaluation had drawn its sample from cataract service providers, cataract patients and the heads of eye department in Mnazi Mmoja Hospital through convenient and purposive sampling procedures. Findings obtained from questionnaire, interview, observation and documentary review show that the case study hospital has only 39.1% of required skilled personnel. It has modern equipment and machines for quality cataract services. However, keratometer, Bscan and YAG laser were not functioning while antibiotics for post operative and follow up care services were not adequately available to fulfil the requirements of all patients. About 75% cataract patients were not adequately received preliminary care as per guideline. 75.6% of patients received partial assessment for cataract surgical services while by 88.5% were fully assessed for critical events and anticipated variation as per standards. The evaluation conclude that the cataract services offered in the case study hospital was not as quality as expected since it had the following short comings: shortage of qualified human resources necessary for cataract services, shortage of medicines particularly antibiotics; lack of standard service guidelines, dysfunction of critical equipment and machines, and also inability of cataract service providers to adhere to standard guidelines