The Bruins defeated the Maple Leafs 5-4 in overtime after overcoming a three-goal deficit in the third period.
The game in Boston crushed all previous records for any Toronto Maple Leafs playoff game broadcasted on CBC since metered measurement began.
"We're thrilled at how Canadians have overwhelmingly embraced CBC's coverage and joined the yearly tradition that is the Stanley Cup Playoffs on CBC's Hockey Night in Canada," said Julie Bristow, executive director, studio and unscripted programming for CBC. "These audience numbers are a reflection of the passion our country has for this great game and we’re excited to continue to fuel the excitement with two star-studded match-ups in the second round."
Sunday's Game 6 record of 4.5 million viewers lasted only one day. Monday's broadcast for Game 7 also shattered the records for an opening-round game on CBC (3.9 million viewers), and a Maple Leafs playoff broadcast on CBC (4.27 million).
The Toronto-Boston matchup became the most-watched first-round series in CBC history, averaging an audience of 3.53 million viewers.
Monday's game reached 40 per cent of the population in Canada, according to ratings data from the Bureau of Broadcast Measurement.
Online coverage of the series on CBCSports.ca also experienced an audience boost compared to last year's opening round, with a 22 per cent increase in average daily unique visitors and 18 per cent increment in average daily page views.Suggest a correction