The 85-year-old TV presenter, who co-hosts alongside Tess Daly, will be replaced by Claudia Winkleman on Saturday night's live show, according to a brief statement on the show's official Twitter account today.
Sir Bruce has hosted the show since it launched in 2004.
It said: "Poor Sir Bruce has flu and so Claudia will be hosting alongside Tess tomorrow at 6.20 pm on @BBCOne. Let's all wish Brucie a get well soon!"
An additional statement released by BBC said: "Sir Bruce Forsyth has the flu and therefore isn't feeling well enough to present tomorrow's Strictly Come Dancing on BBC One. The show looks forward to his return next week."
Claudia usually hosts the Sunday night results show.
This weekend's Strictly Come Dancing will see all fifteen celebrities and their dancing partners take to the dancefloor for their second live performances – but this time they'll be dancing for survival as one couple will be eliminated on Sunday night.
The dances and songs for the episode were revealed earlier this week:
- Ashley and Ola will be performing the American Smooth to 'Beyond the Sea' by Robbie Williams.
- Abbey and Alijaz will Cha Cha to 'Let's Get Loud' by Jennifer Lopez.
- Patrick and Anya will be performing the Tango to the Michael Jackson classic 'Beat It'.
- Rachel and Pasha will Salsa to Daft punk's World-wide hit 'Get Lucky'.
- Dave and Karen will be perform the American Smooth to 'How Do You Like Your Eggs in the Morning?' by Dean Martin and Helen O'Connell.
- Fiona and Anton will Cha Cha to 'Beggin' by Madcon.
- Vanessa and James will be Waltzing to the beautiful 'Run To You' by Whitney Houston.
- Julien and Janette are performing the Tango to Lady Ga Ga's 'Applause'.
- Deborah and Robin will Cha Cha to Aretha Franklin's 'Respect'.
- Sophie and Brendan will be dance the Charleston to 'Rock It To Me' by Caravan Palace.
- Mark and Iveta will Salsa to 'Bom Bom' by Sam and the Womp.
- Tony and Aliona will perform the Charleston to 'It Don't Mean A Thing (If Ain't Got That Swing)' by Chantz.
- Susanna and Kevin are performing the Tango to Bruno Mars' 'Locked Out Of Heaven'.
- Ben and Kristina are waltzing to 'What The World Needs Now' by Dionne Warwick.
- Natalie and Artem will Waltz to 'If I Ain't Got You' by Alicia Keys.
Strictly Come Dancing continues Saturday night (5 October) at 6.20pm on BBC One.
Check out pictures of the full Strictly lineup below:
Copyright: BBC/Ray Burmiston