The Bafta award-winning drama drew an average audience of 7.3 million, or 7.6 million if you include ITV+1.
However, it was not the most-watched programme on Monday night.
That honour went to Coronation Street, which drew a peak audience of 8.3 million for a storyline about the disappearance of 8-year-old Max Turner.
The original series of Broadchurch, which stars David Tennant and Olivia Colman, was a critical and ratings hit.
The mystery followed the investigation into the death of 11-year-old Danny Latimer.
The first episode of the original series was watched by 6.8m viewers but by the end of its run the audience had built to 8.7m (8.9 million peak).
In an unusual move, ITV did not release any previews of the first episode of the new series to stop leaks about the new storyline.
The new series sees the addition of Charlotte Rampling and Marianne Jean-Baptiste to the cast.
Written by show creator Chris Chibnall, the first episode has so far garnered positive reviews.
Andrew Billen in The Times gave the episode five out of five saying it was "expansively told and imaginatively filmed".
He added: "with an extraordinary ensemble cast that churns the narrative like waves in a harbour, Broadchurch will this time free us with nothing but the truth".
Marking the show four out of five, Ben Lawrence in The Telegraph said: "Broadchurch continues to be a rich and complex tapestry which respects the viewer's intelligence and commands you to become an armchair detective.
"Let's hope the momentum can be maintained."
Ellen E Jones in The Independent added: "If Chibnall's aim was to whip us all into a frenzy of anticipation, it worked.
"Episode one was a brilliant demonstration of the risks a writer can get away with when there's a proven cast to fall back on, but the real test comes later. Will nine million of us still be watching in eight weeks time?"
We certainly will, said Mark Lawson in The Guardian.
"Chibnall has gathered enough old loose ends and intriguing new strands to suggest that Mondays may again become a bad night for the nation's pubs and restaurants," he wrote.
The much-anticipated return of ITV drama Broadchurch was seen by a peak audience of eight million viewers according to overnight figures.