Background: Most workers are exposed to a variety of hazards in their workplace. Devising a comprehensive checklist and developing an index for Occupational Safety and Health (OSH) assessment could be useful. This study was conducted in a heavy automotive company with the aim of developing and validating an OSH assessment index.Methods and Materials: We used the experiences and comments of OSH experts to devise a checklist for OSH assessment. Weighting various harmful factors was done using Analytical Hierarchy Process (AHP) technique. Intra-class Correlation Coefficient (ICC) was applied to measure the reliability of the checklist (SPSS version 20). In the studied industry, 150 workstations were assessed using the developed comprehensive checklist. In order to validate the total index, we assessed its correlation with 4 groups of occupational statistics (i.e. accident frequency, severity rates, lost working time rate, and occupational disease incidence rate). A p value of < 0.05 was considered significant.Results: Among 7 sub-indices, sub-indexes of occupational health and the workplace order (w=0.21) and housekeeping (w=0.04) had the highest and the lowest AHP weights, respectively. The mean of ICC was found to be 0.978. The total index (OSHITotal) and the Accident Severity Rate (ASR) had a strong inverse significant correlation (r = -0.774, P=0.002).Conclusion: The developed index covered important occupational hazards. The inter-evaluator reliability for this index was high.