The amount of time patients spend on services to be delivered in clinics still is a major problem for some health centers. To solve this problem, various methods were proposed by researchers. Failure Mode and Effects Analysis (FMEA) is one of the most used approaches to identify influential failure modes in prolonging waiting time. In the FMEA method, numeric scores assign to failure modes using the Risk Priority Number (RPN), but RPN is criticized for its shortcoming and leads to unreal results. In this paper, to cover the conventional FMEA shortcoming, firstly, eleven risk factors result in the prolongation of waiting time introduced by experts. Secondly, integrating the triangular fuzzy number (TFN) with the Best Worth Method (fuzzy-BWM) was utilized to determine the weights of effective criteria. In the following, failure modes ranked through fuzzy Multi-Objective Optimization by Ratio Analysis (fuzzy-MOORA). Finally, the ranks of eleven failure modes were compared in three different methods (Conventional FMEA, conventional MOORA, and fuzzy-MOORA). The potential usage of this method is covering the shortcoming of previous methods and contributing certainty in identifying significant failure modes of the patient waiting for time reduction in Out-Patient Departments (OPD). According to the analysis, three main failures in managing waiting time are: the patients never follow up for a later date by the center, which can result in chaos in OPD because of phone or in-person referrals. Secondly, they are unable to manage to cancel/postpone an appointment in emergency cases; thirdly, office visits are not done in the estimated time, which results in a disordering in the center.