Introduction: Adherence is poor among patients taking antihyperglycemic agents (AHAs) for type 2 diabetes mellitus (T2DM). Inadequate adherence has been linked to decreased glycemic control and increased healthcare costs and hospitalizations. We examined the impact of real-world adherence on glycemic control in T2DM patients treated with canagliflozin. Methods: This retrospective study used US administrative claims data from commercial and Medicare Advantage healthcare enrollees. Study subjects were adult T2DM patients with baseline HbA1c >= 7.0% and a pharmacy claim for canagliflozin between April 01, 2013 and August 31, 2014. Outcomes included treatment patterns, HbA1c reductions and goal attainment, pharmacy costs, and patient characteristics. Adherence, measured by the proportion of days covered (PDC), was calculated as the number of days of canagliflozin availability divided by the length of the follow-up period. Results were analyzed overall and compared between patients who were highly adherent (HA) (PDC >= 0.8) versus less than highly adherent (LHA) (PDC < 0.8). Results: The study population included 2261 patients. At the end of follow-up, patients had an overall mean reduction in HbA1c of 0.97%. Those HA had larger reductions in HbA1c than those LHA (1.17% versus 0.73%, respectively, p < 0.001); 24.6% and 59.4% of patients achieved HbA1c goals of < 7.0% and < 8.0%, respectively. Highly adherent patients were more likely to achieve goals than those LHA. Less than highly adherent patients increased insulin use by 5.4% in the follow-up period, while HA patients decreased the use of most oral AHAs and had no change in insulin use. Conclusions: Patients had an HbA1c reduction of 0.97% in the 12 months following the first canagliflozin fill. Highly adherent patients achieved a greater reduction in HbA1c at the end of the follow-up period and were more likely to reach HbA1c goals. Highly adherent patients also had reductions in the use of most oral AHAs, while LHA patients saw a small increase in insulin use.