Background Physiotherapists (PTs) have an essential role in the facilitation of patients' mobilization after lumbar spinal fusion (LSF). The aim of this study is to investigate whether PTs can predict one-year post-surgery outcome based on their first meeting with the patient immediately after LSF. Method A prospective cohort study with one-year follow-up was conducted. In the first days after surgery, the PTs from hospital wards were asked to predict the patients' overall LSF outcome one year after surgery. One year after surgery, the patients received a questionnaire including the Oswestry Disability Index (ODI), visual analogue scales (VAS) for leg and back pain, quality of life survey (EQ-5D-3 L), global perceived effect (GPA), and satisfaction with surgery outcome (SSO). Univariate and logistic regression were used to calculate the associations between the prognosis and predictive values. Results The study included 170 patients. The analyses showed a significant association between the PTs' prognosis and the primary outcome ODI (p < .01), VAS leg and back, EQ-5D-3 L, and GPE one-year post-surgery (p