ObjectiveTo examine physician factors associated with practice-level uptake of virtual mental healthcare for children and adolescents.Design, setting and participantsA population-based data linkage study of a cohort of all physicians (n=12 054) providing outpatient mental healthcare to children and adolescents (aged 3–17 years, n=303 185) in a single-payer provincial health system in Ontario, Canada from 1 July 2020 to 31 July 2021.ExposuresPhysician characteristics including gender, age, specialty, location of training, practice region, practice size and overall and mental health practice size.Main outcomesPractice-level proportion of outpatient virtual care provided: (1) mostly in-person (<25% virtual care), (2) hybrid (25%–99% virtual care) or (3) exclusively virtual (100% virtual care). Multinomial logistic regression models tested the association between practice-level virtual care provided and physician characteristics.ResultsAmong physicians, 1589 (13.2%) provided mostly in-person mental healthcare with 8714 (67.8%) providing hybrid care, and 2291 (19.0%) providing exclusively virtual care. The provision of exclusive virtual care (vs mostly in-person) was associated with female sex (adjusted OR (aOR) 1.97, 95% CI 1.70 to 2.27 (ref: male)), foreign training (aOR 1.27, 95% CI 1.07 to 1.50 (ref: Canadian-trained)), family physicians (aOR 2.05, 95% CI 1.56 to 2.69 (ref: psychiatrist)) and reversely associated with large practice size (aOR 0.32, 95% CI 0.25 to 0.40 (ref smallest quintile)). Mostly in-person care was associated with older age physicians (71+ years) and practice outside the Toronto region.Conclusions and relevanceIn a single-payer universal healthcare system that remunerates physicians using the same fee structure for in-person and virtual outpatient care, there is heterogeneity in utilisation of virtual care that is associated with provider factors. This practice variation, with limited evidence on effectiveness and appropriate contexts for virtual care use, suggests there may be opportunity for further outcomes research and guidance on appropriate context for paediatric virtual mental healthcare delivery.