In today's world where competition is increasing, one of the main objectives of the firms is to determine the production costs correctly and to reduce these costs by taking into account the targeted quality standards. Thus, efficiency and sustainable profitability will be ensured. For this, it becomes necessary to choose and apply the most appropriate cost calculation methods that can be used.In this research, it is aimed to determine the product costs of a firm operating in the ready-to wear clothing sector and using the job-order costing method, according to the hybrid costing method and compare them with the current results. For this, the case study method was used. For this purpose, the existing cost data of the firm were rearranged within the framework of the hybrid costing method, and total and unit costs were determined. The results of the hybrid costing method obtained were compared with the results of the job-order costing method. As a result, five out of nine orders resulted in cost reductions, and in others, cost increases. In addition, it was determined that the sales costs determined by the hybrid costing method for the implementation period decreased and the gross sales profit increased.