Recurring
Dan Amboyer as Thad and Chad Weber, twin brothers with strange behavior. Thad was Kelsey's boyfriend, until his death. Afterwards, Chad appeared and began to pursue Kelsey.
Tessa Albertson as Caitlin Miller, Liza's college-age daughter
Thorbjørn Harr as Anton Björnberg, a Swedish writer who got his book signed at Empirical Press. He and Kelsey were having an affair while Kelsey was working on his book.
Paul Fitzgerald as David Taylor, Liza's ex-husband and Caitlin's father
Jon Gabrus as Gabe, one of Josh's nerdy friends
Kathy Najimy as Denise Heller, Lauren's mother
Michael Urie as Redmond, an agent and social media icon
Noah Robbins as Bryce Reiger, a 20-something tech billionaire who is interested in investing in Empirical
Ben Rappaport as Max Horowitz, Lauren's ex-boyfriend
Jay Wilkison as Colin McNichol, a writer who infatuates Kelsey
Mather Zickel as Dr. Richard Caldwell, a doctor who starts a relationship with Diana
Meredith Hagner as Montana Goldberg / Amy, a barista friend of Maggie. She starts working as Maggie's assistant and hooking up with Josh, but he soon discovers that she was copying Maggie's arts.
Aasif Mandvi as Jay Malic, A man who discovers Liza's secret and befriends her
Burke Moses as Lachlan Flynn, a spy novelist who becomes the motive of Zane and Kelsey's quarrel
Jennifer Westfeldt as Pauline Turner-Brooks, Charles' ex-wife, with whom he has two daughters, and who naively believes that they can get back together
Chris Tardio as Enzo, Diana's plumber boyfriend
Phoebe Dynevor as Clare, an Irish citizen who begins dating Josh after Liza's recommendation. She and Josh then plan a green card marriage in Ireland.
Laura Benanti as Quinn Tyler (seasons 5–7), a businesswoman and author who purchases Empirical Press and makes Kelsey the head publisher of Millennial. She later dates Charles.
Janeane Garofalo as Cass Dekenessey (season 7), the dean of a local art school who hires Maggie as an Artist in Residence