Abstract Objective To assess changes in juvenile idiopathic arthritis (JIA) treatments and outcomes in Canada, comparing 2005–2010 and 2017–2021 inception cohorts. Methods Patients enrolled within three months of diagnosis in the Research in Arthritis in Canadian Children Emphasizing Outcomes (ReACCh-Out) and the Canadian Alliance of Pediatric Rheumatology Investigators Registry (CAPRI) cohorts were included. Cumulative incidences of drug starts and outcome attainment within 70 weeks of diagnosis were compared with Kaplan–Meier survival analysis and multivariable Cox regression. Results The 2005–2010 and 2017–2021 cohorts included 1128 and 721 patients, respectively. JIA category distribution and baseline clinical juvenile idiopathic arthritis disease activity (cJADAS10) scores at enrolment were comparable. By 70 weeks, 6% of patients (95% CI 5, 7) in the 2005–2010 and 26% (23, 30) in the 2017–2021 cohort had started a biologic DMARD (bDMARD), and 43% (40, 47) and 60% (56, 64) had started a conventional DMARD (cDMARD), respectively. Outcome attainment was 64% (61, 67) and 83% (80, 86) for inactive disease (Wallace criteria), 69% (66, 72) and 84% (81, 87) for minimally active disease (cJADAS10 criteria), 57% (54, 61) and 63% (59, 68) for pain control (<1/10), and 52% (47, 56) and 54% (48, 60) for good health-related quality of life (≥9/10). Conclusion Although baseline disease characteristics were comparable in the 2005–2010 and 2017–2021 cohorts, cDMARD and bDMARD use increased with a concurrent increase in minimally active and inactive disease. Improvements in parent and patient-reported outcomes were smaller than improvements in disease activity.