Viewership was down slightly from last year's Game 1, which earned a 10.6.
That basketball action boosted Jimmy Kimmel, who scored a rating of 3.1 in Nielsen's 56 metered markets, reaching its second highest rating this season, behind "Jimmy Kimmel Live: Behind the Scandalabra" last month.
Kimmel also earned a rating of 1.5 among key 18-to-49-year-olds, based on Nielsen's 25 local people meter markets.
That put Kimmel ahead of Jimmy Fallon's "Tonight Show" in both measures for the first time ever.
Precise viewership and demographic figures for the Spurs-Heat game won't be available until later Friday because Nielsen's "fast affiliate" numbers don't adjust for time zones, and the game started before prime time on the West Coast and after on the East Coast.
Still, it's safe to say ABC dunked over the competition, averaging 10.6 million viewers across prime time and earning a rating of 4.2 in the 18-49 demographic, in which a ratings point equals about 1.3 million viewers. In 18-49, ABC beat the combined rating for Fox, NBC, CBS and the CW.
While CBS and the CW were all in rerun mode, NBC saw a respectable hold from "Last Comic Standing," which fell 13% from last week to a 1.4. Back-to-back episodes of "Undateable" fell 23% from last week's premiere.