BACKGROUND The Tampa Scale of Kinesiophobia (TSK) is a commonly-used measure for the assessment of fear of movement beliefs in chronic complaints, but its responsiveness in subjects after lumbar fusion has been never reported. AIM Evaluating the responsiveness and minimal clinically important differences (MCIDs) for the TSK and its subscales after lumbar fusion. DESIGN Population-based cohort study. SETTING Secondary care rehabilitation hospital. POPULATION In-patients undergoing rehabilitation after lumbar fusion. METHODS At the beginning and end of a four-week motor and cognitive-behavioral rehabilitation program, 180 patients completed the TSK. After the intervention, the global perceived effect (GPE) was analyzed to produce a dichotomous outcome (improved vs. stable). Responsiveness for the TSK and its subscales were calculated by distribution (effect size [ES], standardized response mean [SRM]) and anchor-based methods (receiver operating characteristics (ROC) curves; correlations between change scores of the TSK and its subscales and GPE). ROC curves were also used to compute MCID values. RESULTS The ES ranged from 1.63 to 1.77 and the SRM from 1.25 to 1.39 for TSK and its subscales. The ROC analyses revealed a value of area under the curve (0.999 [95% CI: 0.978; 1.000], 0.998 [95% CI: 0.975; 1.000], 0.990 [95% CI: 0.962; 0.999] for the TSK, Harm and Activity Avoidance subscales, respectively). MCID values greater than 6 (95% CI: >5; >6), 4 (95% CI: >3; >5), and 2 (95% CI: >2; >2) were achieved for the TSK, Harm and Activity Avoidance subscales, respectively. Correlations between change scores of the TSK and its subscales and GPE were high (0.786-0.830). CONCLUSIONS The TSK and its subscales were sensitive in detecting clinical changes in subjects undergoing rehabilitation after lumbar fusion. CLINICAL REHABILITATION IMPACT The obtained MCID values will help in the design of future randomized controlled trials and in the interpretation of the clinical impact of a rehabilitation program after lumbar fusion.