Objectives: Identifying factors predictive of early return to work in patients who underwent a coronary artery bypass graft surgery (CABG). Material and Methods: Two hundred twenty-six working patients who volunteered and underwent a primary coronary artery bypass surgery between September 2013 and May 2014 were selected for the study and followed up for 6 months. Predictors of early return to work (RTW) (within 2 months) were analyzed from variables in a prospectively collected database and the 36-Item Short Form Health Survey (SF-36) questionnaire carried out in the hospital and rehabilitation center as well as from the follow-up performed via the phone. Results: One hundred and two (45.1%) and 155 (68.9%) patients returned to work within 2 and 3 months after the surgery, respectively. Furthermore, 196 patients (87.1%) returned to work within 6 months after the surgery. In the univariate analysis, demographic or socioeconomic factors (such as age, level of education, income), occupational factors (such as occupation type, working hours per week, duration of the preoperative absence from work), psychological factors (such as a patient’s concern about adverse health effects of RTW, feeling depressed, a patient’s attitude towards his/her ability to RTW and a patient’s perception of his/her job stress level) and medical factors (such as serum troponin T and creatine kinase MB (CKMB) level, pump time in surgery, co-surgery and dyslipidemia history) had a statistically significant correlation with early return to work. The patients who early returned to work had significantly higher scores in 3 domains on the SF-36 questionnaire (used for assessing the patients’ quality of life), compared to those who did not return to work early (including physical functioning, role limitations due to physical health and pain). Conclusions: In the present study we identified 4 new medical factors that could be used as predictors of early return to work after CABG. These factors are: normal serum troponin T level, shorter pump time in surgery, normal mean arterial pressure (MAP) before the surgery and higher serum magnesium (Mg) levels. Int J Occup Med Environ Health 2016;29(6):947–957