<p>With rising demand for mental health (MH) services, Internet-based Cognitive Behavioural Therapy (iCBT), involving online modules with minimal, asynchronous therapist support, is a promising alternative to standard, one-on-one CBT (fully-synchronous, scheduled sessions) for treating anxiety and depression, given its flexible delivery and reliance on fewer therapist resources. We leveraged linked, health-administrative data in Ontario, Canada to compare the real-world reach and treatment completion of iCBT and standard CBT. We examined the characteristics (clinical, sociodemographic, health service use) of individuals receiving iCBT via a pilot program (Jan 2020-Aug 2021), compared to those receiving standard CBT. We ascertained who is more likely to receive either modality, and determined the factors associated with treatment completion. We conducted Logistic regression models adjusted for sociodemographics, baseline depression (PHQ-9) and anxiety (GAD-7), and outpatient and acute MH-related service use one year prior to enrollment. Among N = 167 individuals enrolled in iCBT and N = 300 controls receiving standard CBT, a fully-adjusted model revealed that older individuals (ORadj = 1.03, 95% CI 1.01–1.04), those with lower baseline anxiety (ORadj = 0.95, 95% CI 0.91–0.99), and those with a prior MH-related emergency department visit or hospitalization (ORadj = 2.35, 95% CI 1.21–4.53) were more likely to receive iCBT. Over half of participants completed more than the median number of possible treatment sessions/modules (52.7% and 59.0%, respectively) and about one third completed &gt; 75% (33.5% and 33.3%). Clinical and demographic differences, as well as the degree of treatment adherence between clients receiving iCBT vs. standard CBT in a real-world setting were minimal, suggesting that iCBT modalities may hold promise for addressing access-to-care barriers at a population level.</p>