The Golden State Warriors' overtime victory over the Cleveland Cavaliers on Thursday night averaged a 10.6 rating.
ESPN said Friday that the nearly 17.8 million viewers were up 21 percent from the almost 14.7 million for the Finals opener last year between the San Antonio Spurs and Miami Heat.
Ratings represent the percentage of U.S. homes with televisions tuned to a program.
ABC and ESPN are both owned by The Walt Disney Company.
Information from The Associated Press was used in this report.
Warriors win Game 1 in OT
Stephen Curry scores 26 points and the Warriors hold the Cavs to two points in overtime to win Game 1 of the NBA Finals 108-100.