Last year's final played out across two programmes, the first getting 2.6 million and the second 2.7 million.
This year's series, which started on 9 June and is sponsored by skincare brand Freederm, averaged 2.5 million viewers.
The 'BB' experience is due to continue until Friday 10 September in the shape of 'Ultimate Big Brother'.
This features former 'Big Brother' and 'Celebrity Big Brother' contestants along with this year's winner Josie Gibson.
Among them are Ulrika Jonsson, Coolio, "Nasty" Nick Bateman and Chantelle Houghton.
Last night's three-hour show earned a 17.7% share of viewing and was the most watched show in the 9pm-10pm slot, with around 4.25 million viewers.
It beat BBC One's 'The Deep', which managed 3.47 million viewers including BBC HD ratings, a fall from its debut figure of 5.3 million, and ITV1's 'The Bill' attracted an audience of 3.41 million.
While 'Big Brother' may be revived by Channel Five under Richard Desmond, 'The Bill' is set to leave TV screens for good next week.
Five's 9pm-10pm offering last night, the first of a three-part 'CSI' marathon attracted 1.55 million, while BBC Two's 'Treasures of the Anglo Saxons' managed 2.02 million.
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