Background: MANGANESE (Mn) is an essential element for the human body, but it can cause adverse effects on the Central Nervous System at high doses. Exposure to MANGANESE fumes during welding can harm welders' health. Objectives: The current study aimed to measure MANGANESE produced by shielded metal arc welding (SMAW) in the breathing zone air and blood of welders and investigate the relationship between MANGANESE concentrations in air and blood. Methods: In this descriptive-analytical cross-sectional study, 35 welders were enrolled as the exposed group and 40 office workers as the control group. MANGANESE concentration in air was measured according to NIOSH method 7301. Air and blood sample analyses were carried out by ICP-OES. Statistical analysis was performed with MINITAB 17. Data were analyzed using Pearson correlation coefficient, one-sample t-test, paired t-test, and logistic regression. The significance level was set at P < 0. 05. Result: The mean concentration of welding respirable particles and MANGANESE fumes were 9. 56-1. 67 and 0. 45-0. 08 mg/m, three and 22 times the exposure limit recommended by ACGIH, respectively. Average MANGANESE was significantly higher in the welders' blood (0. 16-0. 02 , g/mL) than in the controls' blood (0. 04-0. 002 , g/mL). There were strong and significant correlations between the welding respirable particles and MANGANESE concentration in welders' breathing zone and blood MANGANESE levels. Also, with each year of work experience, the MANGANESE concentration in the welders' blood increased by 1. 5%. Conclusions: Welders are at risk of contamination with MANGANESE. MANGANESE exposure reduction through more efficient ventilation systems, reducing welder's exposure time, staff training, and appropriate respiratory protection equipment should be applied to reduce MANGANESE exposure among welders and prevent health complications.