In 2018, TNFα inhibitors were the highest cost drug class for Canadian public drug programs. In 2019, two Canadian provinces announced mandatory nonmedical switching policies in an attempt to reduce their costs by increasing biosimilar uptake. The national impact of similar policies across Canada is unknown. We conducted a cross-sectional analysis of monthly publicly funded prescription claims for infliximab, etanercept, and adalimumab between June 2015 and December 2019. We reported the market share of biosimilars for infliximab and etanercept in 2019 for each province and estimated the cost savings that public payers could have realized in 2019 if mandatory switching policies had been implemented across Canada, including a sensitivity analysis, which assumed that governments receive a 25% rebate on all biologics. Provincial drug programs spent CAD $991.84 million on infliximab, etanercept, and adalimumab in 2019, and, when biosimilars were available, they constituted only 15.5% of national utilization of these drugs. In British Columbia, the implementation of a mandatory switching policy for patients with rheumatic conditions increased the biosimilar market share of infliximab and etanercept by 299% (from 19.7% to 78.5%). If applied nationwide to all three biologics for all indications, we estimate such policies could lead to annual savings of between CAD $179.71 million and CAD $425.64 million nationally. The overall market share of biosimilars remains low in all provinces where mandatory switching policies have not been introduced. The cost implications of successfully increasing biosimilar uptake would be substantial, particularly as more biosimilars reach the Canadian market.