Baldwin, who most recently starred in the Broadway revival of Finian's Rainbow and will soon depart for the London world premiere of the Hal Prince musical Paradise Found, is the first to be cast in the two-person musical about love and marriage.
As previously reported, Susan H. Schulman (The Sound of Music, Sunset Boulevard, Little Women) will direct the production that runs Aug. 10-28. I Do! I Do! spans 50 years in the marriage of its central characters, Agnes and Michael.
Additional casting and creative duties will be announced shortly.
The complete Westport season follows: She Loves Me (April 20-May 8); Dinner with Friends (June 1-19); Happy Days (July 6-24); I Do! I Do! (Aug. 10-28); and The Diary of Anne Frank (Sept. 28-Oct. 16).