Raonic opened his 2021 campaign at the 2021 ATP Cup representing team Canada alongside countrymen Denis Shapovalov, Steven Diez and Peter Polansky. Canada was drawn into a round robin group with teams Serbia and Germany, and Raonic was penciled in as the number 2 player. In the first tie against team Serbia, Raonic won his singles match in straight sets over Dusan Lajovic. Partnering with Shapovalov in the deciding doubles match, they were unable to get the win and thus lost the tie 2–1. In the second tie, versus team Germany, Raonic lost his singles match against Jan-Lennard Struff in two tiebreaker sets, and after Shapovalov lost his match against Zverev, Canada was officially eliminated from the tournament.