This marks an increase from the 2019 series opener, which launched to an average audience of 7.8 million people.
Saturday night’s episode achieved a 42.2% audience share and had a peak audience of nine million viewers, a spokesman for the programme said.
The launch saw a celebrity perform as part of a same-sex pairing for the first time in the programme’s history.
Among this year’s contestants are former home secretary Jacqui Smith, comedian Bill Bailey and actress Caroline Quentin.
Former boxer Nicola Adams will be the first celebrity to compete in the contest as part of a same-sex pairing.
The programme is being judged by Craig Revel Horwood, Motsi Mabuse and Shirley Ballas.
Adams tweeted to say she is “so excited” to have announced her partner, Katya Jones.
“I couldn’t have been paired with a better partner than a fellow champ in her own right and I can’t wait to see what creative dance routines Katya comes up with,” she wrote.
“Are you ready for the first dance?”
Contestant and actress Caroline Quentin said she dreamed of being a dancer when she was a child.
She said: “I went to ballet school as a little girl, I loved it and my dream was to become a ballerina.
“In truth I wasn’t quite good enough.
“I was a little bit short and a little bit round and I have always had a kind of longing to see if I could be better at it.”
Quentin, 60, has been partnered with Johannes Radebe.
She said she is “beside herself with joy” to have been paired with the professional dancer.
Former home secretary Jacqui Smith, 57, will team up with Anton Du Beke.
She said: “I’m completely out of my comfort zone but I’m going to prove that even when you are in your late 50s you can learn new things and find joy in a new adventure.”
EastEnders actress Maisie Smith, 19, will be the partner of Gorka Marquez.
At the end of the programme, the couples took to the dance floor for the first time for a group performance.
The dancers remained in their pairings throughout the routine due to coronavirus regulations.