Patients undergoing lumbar discectomy are typically referred for postoperative rehabilitation. However, evidence regarding effectiveness of postoperative rehabilitation to improve surgical outcome and hasten return to work is scarce with conflicting results in the published literature. This study investigates the effect of postoperative rehabilitation on return to work, duration of sick leave and working ability after surgery for lumbar disc herniation. Single center randomized controlled trial. Patients scheduled for primary discectomy due to lumbar disc herniation were included in the study. Self-reported measures included working ability, work status, and job type defined by the International Standard Classification of Occupations. All outcomes including duration of sick leave were obtained from follow-up questionnaires at 1 and 2 years after surgery. This is a secondary analysis from a randomized controlled trial comparing patients who were referred to rehabilitation at the municipal facility starting 4–6 weeks postoperative (REHAB) and patients sent home after surgery without any planned rehabilitation course (HOME). Linear regression was performed to identify baseline characteristics associated with duration of sick leave. One hundred forty-six patients were included and equally distributed between the groups. Follow-up rate was 78% after 1 and 2 years. Both groups had a similar postoperative sick leave period of approximately 9 weeks. After 1 year 79% had returned to work in the HOME-group versus 74% in the REHAB-group, which was not statistically significant. Working ability improved from baseline to 1 year in both groups and this improvement was sustained at 2-year follow-up. Stepwise linear regression showed that preoperative duration of leg pain and working ability was associated with duration of postoperative sick leave. Referral for unstandardized municipal rehabilitation does not affect duration of postoperative sick leave, return to work or working ability in patients recovering after surgery for lumbar disc herniation. Duration of preoperative leg pain and preoperative working ability was significantly associated with the duration of postoperative sick leave.