Objective: Hospital managers need to have accurate information about actual costs to make efficient and effective decisions. Activity-based costing (ABC) is put forward as an alternative, more accurate costing method to calculate the cost of medical treatment. The objective of this paper is the application of an activity-based method to estimate the cost of cataract surgery in an ophthalmic hospital. Methods: The present descriptive-analytical study was carried out at an ophthalmic hospital, in February and March of 2021, in Iran. Surgical operations for cataracts were considered. The required data were collected through conducting interviews with experts and relevant units, direct observation of activities, analysis of documents in the financial department, and the hospital information system (HIS) and financial software system of the hospital. The cost of surgical operations was estimated by activity-based costing (ABC). Results: According to the findings, the amount and the share of the total costs of the activities identified in the main centers were as follows: human resources 54.24% of the total cost of cataract surgery which is the highest share of surgery costs; the cost of consumables was 32.57% of the total cost of cataract surgery is the second share of surgery costs. Conclusions: The research results showed that in this regard administrators should design and implement a comprehensive operational planning system in the hospital.