This single-center, retrospective study aims to analyze the sociodemographic, injury characteristics, and the total number of lost working days of patients undergoing hand flexor tendon repair and to identify factors predicting reoperation.Hand flexor tendon repairs conducted using a four-strand modified Kessler core suture with early rehabilitation from January 2013 to December 2016 were included in this study. The variables evaluated in this study were patient sociodemographic and injury characteristics, number of lost working days, and reoperations because of rupture and/or adhesion formation. Injury severity was determined using Modified Hand Injury Severity Scoring (MHISS). Binary logistic regression analysis was conducted to identify the predictors of reoperation.A total of 194 patients were included in this study, who had experienced 329 tendon injuries. Participants were young (mean age, 31.8), mostly male (79.4%), and mostly blue-collar workers (50.0%). Most patients had a zone 2 injury affecting a single digit of the dominant hand. The mean MHISS value was 46.6, and the mean time to return to work was 114.0 days. A total of 37 (19.1%) patients required reoperation because of rupture and/or adhesion formation. Smoking, zone 2 injury, and high MHISS value were negative predictors of reoperation.To minimize the need for reoperation, surgeons and rehabilitation teams should take special care of patients with zone 2 injuries, high MHISS values, and smoking history.