It comes as regular judge Bruno Tonioli is unable to take part due to ongoing uncertainty over international travel restrictions during the Covid-19 pandemic.
Du Beke joined the judging panel during the 2020 series for a two-week stint, but will now become a permanent fixture during the 2021 series.
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The professional dancer said: "My loves I cannot tell you how thrilled I am to be stepping into Bruno’s brogues for the next series of Strictly.
"It’s a dream come true to be judging alongside the best of the best and I promise to be kinder to all the couples than any of them have ever been to me."
Du Beke joins the returning judging panel of Craig Revel Horwood, Motsi Mabuse and Shirley Ballas.
Tonioli is based in the US as a judge on American series Dancing With The Stars.
The BBC said he "will be unable to take part in the series this year" as a result due to Covid.
Tonioli said: "While I am gutted to not be on the show this year, there is one person and one person only that could take my place – it’s just a shame they weren’t available… haha! Darlings I’m kidding, I’m kidding!
"Seriously though, I have to tell you, Anton IS Mr Strictly and if anybody is filling in for me, it has to be him. I honestly wouldn’t have it any other way and I am so excited to see him waggle his paddle."
Du Beke is the longest-serving professional dancer having been a fixture on the BBC One series since it began.
The BBC said further details regarding the upcoming series of Strictly Come Dancing would be announced in due course.
Comedian Bill Bailey won last year's competition with Oti Mabuse.