Background: The International Duration Evaluation of Adjuvant Chemotherapy (IDEA) collaboration showed no significant clinical difference in outcomes in patients with stage III colon cancer treated with 3 months versus 6 months of oxaliplatin-based adjuvant chemotherapy (O-ACT). We aimed to assess the change in practice patterns of ACT before and after publication of the IDEA study. Methods: This was a retrospective, population-based, cohort study of patients ≥ 18 years of age diagnosed with stage III colon cancer between January 1, 2012 and December 31, 2021 in Alberta, Canada. Eligible patients received >1 dose of ACT. Patients were divided into two groups; pre-IDEA (diagnosed prior to March 31, 2018) and post-IDEA (diagnosed on or after April 1, 2018). Treatment duration was categorized as short (<4.5 months) and long (≥4.5 months). The primary outcome was the median duration and type of ACT and factors associated with a shorter duration of ACT. Two-year overall survival (OS) and cancer-specific survival (CSS) were secondary outcomes. Results: We identified a total of 735 patients. Median age at diagnosis was 64 years (range 27-90 years) and 52.8% (N=388) were male. 48.8% (N=359) patients had had pT4 and/or pN2 disease. 78% (N=572) received O-ACT. In the post-IDEA era, the use of capecitabine plus oxaliplatin (CAPOX) ACT increased (23.0% to 50.9%, p<0.001) and median duration of O-ACT was significantly shorter (2.7 vs 4.8 months, p<0.001). On multivariable logistic regression, factors associated with shorter duration of ACT included treatment in the post-IDEA era (odds ratio [OR] 1.85, p=0.007), no pT4 and/or pN2 disease (OR 1.6, p=0.02), and receipt of CAPOX ACT (OR 2.7, p<0.001). Characteristics not significantly associated with ACT duration included age, sex, residence rurality, neighborhood income, and comorbidity index. The 2-year OS and CSS was similar in the pre-IDEA and post-IDEA eras (OS 95% vs 93%, p=0.29; CSS 96% vs 96%, p=0.30). Neither time era or treatment duration were independently associated with OS or CSS in multivariable models. Conclusions: Our study is one of the first that shows that the results of the IDEA trial have been largely adopted in clinical practice with shorter duration of ACT and increased use of CAPOX ACT in low-risk stage III colon cancer using population-based data.