Introduction. The landscape of childhood diabetes has evolved and addressing the knowledge gaps in non-Type 1 diabetes mellitus are key to accurate diagnosis. Objectives. A national surveillance study was completed between 2006 and 2008 and then repeated between 2017 and 2019 to describe Canadian incidence trends and clinical characteristics of non-Type 1 diabetes mellitus. Methods. We prospectively tracked new cases of non-Type 1 diabetes mellitus in children <18 years of age between June 1, 2017 and May 31, 2019. For each reported new case, a detailed questionnaire was completed, and cases were classified as Type 2 diabetes mellitus, medication-induced diabetes (MID), monogenic diabetes, or “indeterminate.” Minimum incidence rates and 10-year incidence trends of non-Type 1 diabetes mellitus and its subtypes were calculated. Results. 441 cases of non-Type 1 diabetes mellitus were included (Type 2 diabetes mellitus = 332; MID = 52; monogenic diabetes = 30; indeterminate = 27). Compared to 10 years ago, the incidence of MID and monogenic diabetes remained stable, while Type 2 diabetes mellitus increased by 60% ( p < 0.001 ) overall and by 37% ( p = 0.005 ) and 50% ( p = 0.001 ) in females and males, respectively. Type 2 diabetes mellitus incidence increased by 1.5 times in Indigenous ( p < 0.001 ) and doubled in Asian ( p = 0.003 ) children. Conclusions. Canadian incidence rates of childhood-onset Type 2 diabetes mellitus have significantly increased. Further research, policy, and prevention efforts are needed to curb rising rates of youth onset Type 2 diabetes mellitus.