Purpose: Examining whether socio-demographic variables, pain or functionality are related to the degree of clinic-based therapy adherence in patients suffering from nonspecific chronic spinal pain (nCSP). Design: Secondary analysis of a randomized clinical trial. Setting: University hospital of Ghent and Brussels. Methods: Dutch speakers, 18–65 years old, experiencing nCSP for at least 3 months. 120 participants were randomly allocated to two interventional groups, of which 94 completed all therapy sessions. Main outcome measures: Degree of clinic-based adherence, defined as the amount of completed therapy sessions. Results: Demographic data (sex, age or education) were not significantly associated with adherence in the total sample or the neuroscience group. For the traditional physiotherapy group, educational level was associated with attendance of at least 50% of the therapy sessions. Regarding pain-, belief- and function-related measures, only the association between change in kinesiophobia and adherence was significant for the traditional physiotherapy group. Conclusions: Factors related to therapy adherence in the total group or the neuroscience group could not be found. Educational level and change in kinesiophobia were however related to therapy adherence in the traditional physiotherapy group.