Background and aims: Today, shift working is common in many developed countries cause industrial development and implement of service organization. This study attempts to determine the relationship between shift working and blood parameters among employees of a petrochemical company. Methods: In a cross-sectional design, the study was performed with 403 workers from a petrochemical company, Iran in 1394. Employees were divided into two groups of day working and shift working. Blood samples were taken from participant in the workplace by expert. For more accurate of assess alters metabolism in body, hematological indexes were analyzed for fasting plasma glucose, triglyceride, cholesterol, LDL, HDL, liver enzymes such SGOT, SGPT and complete blood cell. Blood pressure were taken from both day workers and shift workers by standard method. The mean of these parameters was compared in two groups. Results: The mean age of participants in this study was 32.02±7.6 years, the mean age of day workers 33.16±8.3 years and shift workers was 31.5±7.3 years. The group with age higher than 50 years old had the highest average systolic blood pressure 11.71±0.61 mm/Hg and diastolic blood pressure 7.2±0.69 mm/Hg compare to the other aged groups. The results of statistical tests showed significant difference between the systolic and diastolic blood pressure in the day and shift working people (p<0.05). The mean of SGPT in shift workers were lower than day workers, while no significant difference was seen between liver enzymes SGOT and SGPT in two groups (p>0.05). The mean of RBC and WBC in day workers were higher than shift workers, but did no showed significant difference between RBC and WBC in two groups (p>0.05). The statistical tests results showed significant difference between the glucose, triglyceride, cholesterol and LDL in the day workers and shift workers (p<0.05). Also, significant difference was seen between MCV, RBC and SGPT with systolic blood pressure in shift workers (p<0.05). Conclusion: The circadian rhythm and metabolic indices can be changed by shift working, resulting in significantly more risk factors for cardiovascular disorders and digestive problems. © 2015 Tehran University of Medical Sciences and Health Services. All rights reserved.</p>