Background: Due to high prevalence of musculoskeletal risk factors among kitchen workers and their role in causing discomfort, the aim of this study was to investigate the effects of ergonomic factors (mental workload and working posture) on musculoskeletal disorders (MSDs) among workers of training hospitals in Qazvin, Iran. Materials and Methods: This cross-sectional study was done through census among 60 workers of teaching hospital's kitchens of Qazvin University of Medical Sciences in 2016. Data were collected using pain perception and mental workload questionnaires and Quick Exposure Check (QEC) method was used for posture assessment. Data were analyzed using single and multiple logistic regression tests. Results: About 85% of the workers reported that their work shift was very heavier than normal. The best and worst exposure score in QEC method were assigned to cooking and trolley responsible tasks, respectively. Seventy percent of working postures were classified in action level 3 (i.e. investigation and changes are required soon) that increased the backache prevalence by nearly about 4 times. Heavy workload in interaction with other influential factors increased the neck discomfort about 5 times and back discomfort by 2.5 times. Conclusions: Long working hours, heavy workload, stress, high-speed work, long standing and inadequate rest are the factors influencing the increase of MSDs prevalence among the kitchen workers. By increasing numbers of manpower, reducing the workload and working hours and adequate rest, in addition to doing the work properly, MSDs in this group can somehow be reduced.