Main •
Sutton Foster as Liza Miller, a 40-year-old divorced mother •
Debi Mazar as Maggie Amato, Liza's lesbian artist best friend and roommate •
Miriam Shor as Diana Trout, Liza's temperamental boss, who works as head of marketing at Empirical Press (seasons 1–6; guest season 7) •
Nico Tortorella as Josh, a 26-year-old
tattoo artist who owns his studio •
Hilary Duff as Kelsey Peters, a 26-year-old
book editor at Empirical Press who befriends Liza after they start working together •
Molly Bernard as Lauren Heller, Kelsey's 26-year old friend (seasons 2–7; recurring season 1) •
Peter Hermann as Charles Brooks, head and heir of Empirical Press (season 2–7; recurring season 1)
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 •
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 •
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 •
Richard Masur as Edward L.L. Moore, the writer of
Crown of Kings, one of Empirical Press' biggest-selling novel series, which is a homage to
George R. R. Martin's
A Song of Ice and Fire. The character himself is a homage to Martin, having similarity to Martin's physical traits. •
Lois Smith as Belinda Lacroix, a romance novelist, one of Empirical Press' oldest members. After decades of successful works, she dies during a lunch with Liza, Charles and Diana. •
Jesse James Keitel as Tam, Lauren's personal assistant == Episodes ==