Comcast Corp.’s Universal Pictures said it is making its movies available to watch at home while they are still in theaters, a massive change from Hollywood’s long-established business model that could upend the industry if other studios follow suit.

The decision comes amid widespread closures of movie theaters as the global coronavirus pandemic spreads. Authorities in New York City and Los Angeles on Sunday ordered all movie theaters to close; exhibitors had previously said they would limit attendance in theaters to 50%...