Purpose Continued inability to work has societal and individual consequences. Thus, the factors associated with sustained return to work after lumbar discectomy should be identified. Prior studies of the biopsychosocial factors associated with sustained RTW were primarily based on patient-reported outcome data and have shown conflicting results because of small study samples. In patients undergoing first-time, single-level, simple lumbar discectomy, we describe the time to sustained return to work within 2 years after surgery using outcome data from a national database and identify the pre- and peri-operative factors associated with sustained return to work within 2 years by developing and validating a predictive multivariable model. Methods The time to a sustained return to work within the study period was described using a Kaplan-Meier plot. A temporal validated Cox proportional hazards model examined associations between biopsychosocial factors and return to work. Results In the derivation cohort made up by 351 operated patients who were on sick-leave for more than 3 weeks around the time of surgery, 62% returned to work (median 15 weeks). The probability of sustained return to work was associated with a high education level, positive expectations towards future labor market attachment, pre-operative stable labor market attachment, pre-operative higher physical quality of life, and less disability. Conclusions Through the development and validation of a predictive model, this study identifies a number of patient-related factors associated with sustained return to work after lumbar discectomy, while revealing that most disease-related clinical findings were not associated with the outcome.