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Background: High blood pressure (HBP) is one of the effective risk factors for many diseases. Hence, a variety of studies have been done for identifying its risk factors which have led to the diagnosis of different factors, among which working on shift work (WSW) can be mentioned. In this longitudinal study, we deal with the effect of WSW on BP by controlling the confounding factors through GEE regression which is a powerful tool for correlational and longitudinal data analysis. Materials and Methods:In this retrospective cohort study, data collection was done through annual observations of health and safety executive (HSE) center of Mobarakeh Steel Company (MSCO) of Isfahan on the workers in 2007-2009. For data analysis, systolic blood pressure (SBP) and diastolic blood pressure (DBP) were regarded as dependent variables, whereas body mass index (BMI), age, education level (EL), and shift work were considered independent variables. SPSS version 15 was used to apply GEE regression to the assessment of parameters corresponding to the factors causing change in SBP and DBP. Results: Of the independent variables, BMI and age had a significant relationship with SBP and DBP however, the results did not indicate any significant relationships between BP and WSW and EL. Conclusion: In this study, there was not a significant relationship between shift work and BP. This can be attributed to the likelihood of SWS being healthier, as well as the flexibility of work hours, income, and more intervals for shift workers in comparison to day workers.