BBC One controller Jay Hunt revealed the appointments this morning, following a month of speculation surrounding the show's replacement for 66-year-old Arlene Phillips.
Dixon, who won the competition in 2007, is a full-time panel member, while Bussell will appear as a guest judge at the end of the series. The professional dancer will also have a role on this year's spinoff show It Takes Two, it has been confirmed.
"As a former Strictly champion, Alesha knows exactly what it takes to win," said Hunt. "Her eye for great performance and her charisma and charm make Alesha a great addition to the judging panel.
"Darcey has impeccable credentials as a dancer and, as a guest judge, she will bring an exciting new dimension to the last few weeks of the Strictly competition."
Speaking about her return to the show, Dixon said: "I'm honoured and excited to be joining the judging panel. I've always felt like part of the Strictly family and really believe in the show."
Bussell added: "It is a real pleasure to have been invited to join Strictly Come Dancing. It is a fantastic show and I'm looking forward to getting to know the dancers and being part of the excitement."
Strictly Come Dancing will air on BBC One in the autumn.
> Arlene Phillips joins 'The One Show'