Monday's first semi-final, which was won by boyband Collabro, pulled in an average audience of 9.12 million (39.1%) from 7.30pm. A further 448k watched on +1.
Figures dropped for the results show at 9.30pm, which pulled in 7.86 million (33.3%). 288k checked out the results on +1.
On BBC One, a Bank Holiday showing of Pirates of the Caribbean: On Stranger Tides attracted 3.07 million (13.1%) at 8pm.
BBC Two's 50th birthday celebrations continued with 1.49 million (6.3%) tuning in for The Fast Show Special at 9pm and 1.49 million (8.0%) sticking around for the Goodness Gracious Me reunion at 10pm.
Channel 4's reality series The Island with Bear Grylls pulled in 1.67 million (7.1%) at 9pm, while What The Dambusters Did Next attracted 1.01 million (4.6%) at the same time on Channel 5.
Elsewhere, Stephen Mulhern's Britain's Got More Talent tickled 695k (4.2%) at 10pm on ITV after the main show.
Meanwhile, the latest Made in Chelsea amused 635k (3.8%) at 10pm on E4.