Through its first two weeks, Season 27 is averaging 4.8M multi-platform viewers across five episodes, up 9% from last summer during that time frame, per numbers shared by Paramount Global that incorporate both Nielsen’s linear data with the company’s internal streaming data.

Big Brother season 27 premiered on July 10 with a 90-minute episode. During the premiere, season 13 winner Rachel Reilly was unmasked as the "mystery Houseguest" who would be joining the contestants in Hotel Mystère. In July 2025, Chen Moonves told Entertainment Weekly that "people should be afraid of [Reilly] and of getting in her crosshairs."