The actress will join stars including Peter Andre and Jamelia, when the show launches next week.
The news was revealed by BBC1 controller Charlotte Moore, at the Edinburgh TV festival, and Helen has shared her joy, stating: “I'm really excited to be joining 'Strictly'. I know it's going to be a challenge and if I'm honest I'm slightly terrified, but I can't wait to get my tan and sequins on!”
While TV fans are most likely to recognise Helen as Nurse Trixie from 'Call The Midwife', she's also starred in 'Hotel Babylon' and 'Scar Tissue'.
There are just two celebs to be revealed ahead of the series' launch, and both will be unveiled on 'The One Show', on Thursday 27 August at 7pm.
Also preparing to get their dancing shoes on are The Wanted’s Jay McGuiness and ‘One Show’ correspondent Anita Rani, boxer Anthony Ogogo, BBC weather presenter Carol Kirkwood, ‘EastEnders’ actress Kellie Bright, singer Peter Andre, broadcaster Jeremy Vine and TV chef Ainsley Harriott.
Former ‘Corrie’ star Georgia May Foote, singer Daniel O’Donnell and newsreader Katie Derham will also be starring in this year's 'Strictly', which returns to BBC1 on Saturday 5 September.