The production, which is directed by Lyndsey Posner (Noises Off, Abigail's Party), will play a limited run at Wyndham's from 16 May to 31 August 2013 (previews from 14 May).
Kendal plays Sheila in the production, which recently played a UK tour, alongside Tointon as Ginny and Jonathan Coy as Philip.
First performed in 1965, Relatively Speaking is a comedy of mistaken identity centring on a complex love triangle between a pair of young lovers and an older married man. It transferred to the West End's Duke of York's in 1967 starring Kendal's Good Life co-star Richard Briers.
Felicity Kendal’s most recent West End credits include Mrs Warren's Profession, The Vortex, Amy’s View, Jumpers, Happy Days, Fallen Angels and Simon Gray’s posthumous The Last Cigarette. She starred in the original West End production of Ayckbourn's The Norman Conquests in 1973.
Former EastEnders star Kara Tointon recently appeared in Ayckbourn's Absent Friends at the West End's Harold Pinter Theatre. She made her West End debut playing Eliza Doolittle in Pygmalion alongside Rupert Everett last year.
Jonathan Coy played Leonato alongside David Tennant and Catherine Tate in Much Ado About Nothing at Wyndham's Theatre in 2011. His many television credits include Hornblower, Rumpole and Foyle's War.