Introduction: Construction industry is one of the dangerous industries with special requirements in the world. Most companies implemented Occupational Health and Safety Management Systems (OHSMS) in order to enhance their health and safety performance, but there are some debates in their effectiveness. The aims of this study were identifying the influential factors on OHSMS success and quantitative evaluation of OHSMS’ effectiveness by Analytical Network Process (ANP) method.

Methods: In this study, relative importance weights of main elements and criteria were determined by ANP method. An OHS performance index was developed by obtained importance weights of elements and criteria.

Results: Policy, management review and planning had the highest importance weights values in OHSMS. They were 0.32, 0.29 and 0.23, respectively. Management commitment, worker participation, allocating financial resource for OHS programs, risk assessment and having report, record and accident investigation system were influential factors in implementation of OHSASA18001.

Conclusion: OHSMS Implementation is a gradual process and influential factors have positive impacts on the effectiveness of OHSMS.