The U.S. television audience for the 90th Academy Awards broadcast on ABC dropped almost 16 per cent from last year.
Preliminary Nielsen data showed that total viewership for the film industry's highest honours could come in below the 2008 record low of 32 million, and follows a rating slide in other award shows and sport events this year as viewers turn to streaming options.
The Olympics and the Super Bowl also suffered double-digit declines.
The Nielsen data does not include viewing of the Oscars on digital and mobile platforms.
Updated numbers will be released later on Monday.