The talent show, created by Simon Cowell, attracted a 40.3 per cent audience share during the 7pm-8.25pm time slot. Cowell is a judge on the panel, alongside Alesha Dixon, Amanda Holden and David Walliams.
But this year’s launch episode fell short of the 10.1 million viewers who watched the first episode of last year’s series.
Since Britain’s Got Talent debuted in 2007, its biggest series launch ratings came in 2014, when 11.1 million viewers tuned in.
Meanwhile, BBC One scored 4.5 million viewers – a 21.1 per cent audience share – for the finale of The Voice.
It is the last time the competitive singing game show will air on the BBC after the rights were sold to ITV.