Background & Objectives: Work-related musculoskeletal disorders caused by poor posture are the most common occupational illnesses. Among all the risk factors of musculoskeletal disorders in assembling industry, this descriptive-analytical study aimed to assess posture of assemblers working in a gas turbine company as well as the effect of training using OCRA method. Methods: At first, a film was taken from work procedure and posture of the operators and then prevalence of upper-limb musculoskeletal disorders was determined for 96 technicians (assemblers) using Nordic questionnaire. Posture score was assigned to each task by OCRA software. Face to face training was provided to assembling workers on doing tasks correctly and the posture was reassessed. Data were analyzed by One Way ANOVA and t-test using SPSS-16. Results: The highest complaints were recorded for wrist and shoulder. Mean OCRA risk scores were significantly different between right and left hands for all cases. There were also significant differences in OCRA risk scores between connection box, piping, connection MBT-MBP, and fasten unit wall job groups. However, risk score index displayed no significant differences between connection MBT-MBP and roof assembly job groups. Total OCRA risk scores of before training significantly differed from those of after trainings. Conclusion: According to the results, OCRA is a useful method for assessment of musculoskeletal disorders in assembly industries. Considering effectiveness of training on decreasing the risks, ergonomic training to individuals is recommended.