The second main series on Channel 5 launched at 9.00pm with an average of 2.6 million viewers, according to overnight ratings data.
It rated the same as Big Brother 12 launch last September, which followed Celebrity Big Brother. The spin-off show, fronted by Emma Willis, followed immediately after and attracted an average of 821,000 viewers.
This is the first time Big Brother is airing during the summer since 2010. It will face a tough summer as the Euro football championships and London 2012 Olympics take centre stage.
Over on ITV 1, The Lemurs of Madagascar with Martin Clunes managed a poor 1.6 million viewers. BBC one topped the 9pm slot with drama Silk attracting 4.7 million viewers.