Although there have been increasing demands for health care providers to take part in inter-professional practices in recent years, very little attention has been paid to the actualization of such practices in the private sector. This study describes private-sector physiotherapists' inter-professional practices regarding low back pain (LBP) management and identifies organizational and provider-level variables associated with the intensity of such practices. A total of 327 randomly selected physiotherapists were surveyed in the province of Quebec. Data were analyzed using descriptive and multiple regression analyses. Physiotherapists reported frequent interactions with other physiotherapists (daily/weekly for 52.6%), family physicians (51.0%), and physiotherapy (PT) assistants (45.2%), but infrequent interactions with psychologists (3.6%), neurosurgeons (0.9%), and chiropractors (0.3%). Frequently reported means of interactions were written and oral messages sent through clients (55.1% and 24.1%, respectively), face-to-face unplanned discussions (41.9%), and faxed or mailed letters (23.2%). Variables associated with the intensity of inter-professional practices (mean of 6.7 [ 1.7] out of 10 on the Intensity of Interprofessional Practices Questionnaire for Private Sector Physiotherapists) were related to physiotherapists' clientele, social activities with other providers, and perceptions of inter-professional practices as well as organizational models, vision, and provision of PT training. There is room to improve inter-professional practices with private-sector physiotherapists involved in managing LBP. Targets for action include physiotherapists and their workplaces.