The series, titled "Happyish," co-stars Kathryn Hahn and Rhys Ifans, the premium cable channel said Thursday.
Hoffman, an Oscar-winning actor for 2005's "Capote," is among a number of big-screen stars choosing to work in television as well.
Billy Bob Thornton, who's starring in an upcoming FX series "Fargo," inspired by the Coen brothers movie, said this week that TV has eclipsed movies as the place for sophisticated fare.
"Every actor is interested in television right now," Showtime President David Nevins told the Television Critics Association on Thursday. "The level of long-form (series) storytelling is very seductive for the talent right now."
Showtime also announced a new drama, "The Affair," starring Dominic West, Ruth Wilson, Maura Tierney and Joshua Jackson. Nevins said the show's intimate approach is in contrast to a TV series trend of bigger and splashier.
During a subsequent Showtime panel on the Matt LeBlanc comedy "Episodes," cast members were asked if actors really prefer TV or actually pine to work in movies.
"I can't get a movie," replied LeBlanc, the former "Friends" star who plays a fictional version of himself in "Episodes."
"Same here," said actress Kathleen Rose Perkins.
LeBlanc then added that "great writing is coming back to television" and he considers it an honor to work with writer-producers David Crane and Jeffrey Klarik, who created the witty satire about Hollywood and two fish-out-of-water British writers, played by Tamsin Greig and Stephen Mangan.
"Episodes" is in its third season and has been renewed for a fourth. "Happyish" and "The Affair" will air in the next year but air dates have yet to be set.