Background: The efficacy and safety of lecanemab have previously been evaluated in the Phase 3 randomized clinical trial, Clarity AD (NCT03887455). Methods: A Markov cohort model was developed to estimate the cost-effectiveness of lecanemab versus standard of care (SoC) in patients with mild cognitive impairment (MCI) or mild dementia due to Alzheimer’s disease (AD), with confirmed beta-amyloid (Aβ) pathology, from a Canadian societal perspective. Health states were determined by Clinical Dementia Rating-Sum of Boxes (CDR-SB) scores. Transitions between health states during month 0-18 were estimated from Clarity AD. Beyond month 18, relative efficacy for lecanemab in the form of the hazard ratio for time-to-worsening of CDR-SB was applied to literature-based transition probabilities. The model included the effects of lost productivity and impact on carer health-related quality of life. Results: The incremental cost-effectiveness ratio (ICER) for lecanemab vs SoC was estimated to be CAD 62,751 per QALY gained. The probability that lecanemab was cost-effective at a threshold of CAD 100,000 was estimated to be 88.5%. Conclusions: Lecanemab represents a cost-effective option for the treatment for early AD from the Canadian societal perspective. The results of this analysis can be used to inform clinical and economic decision making.