Main •
Asa Butterfield as Otis Milburn, a socially awkward teenager who gives sex advice to his peers •
Gillian Anderson as Jean Milburn, Otis's mother and a well-known sex therapist •
Ncuti Gatwa as Eric Effiong, Otis's openly gay best friend who comes from a religious Ghanaian-Nigerian family •
Emma Mackey as Maeve Wiley, an intelligent but troubled teenager who runs a sex therapy clinic with Otis •
Connor Swindells as Adam Groff, the headmaster's son and Eric's bully-turned-love interest •
Kedar Williams-Stirling as Jackson Marchetti, the head boy at Moordale Secondary School and a swimming champion •
Alistair Petrie as Michael Groff, the headmaster of Moordale Secondary School and Adam's strict father •
Mimi Keene as Ruby Matthews, a popular girl at Moordale Secondary School and the leader of the Untouchables clique •
Aimee Lou Wood as Aimee Gibbs, a former member of the Untouchables who becomes friends with Maeve •
Chaneil Kular as Anwar Bakshi (series 1–3), a member of the Untouchables •
Simone Ashley as Olivia Hanan (series 1–3), a member of the Untouchables •
Tanya Reynolds as Lily Iglehart (series 1–3), a girl who writes alien erotica •
Patricia Allison as Ola Nyman (series 1–3), a
pansexual girl who joins Moordale Secondary School •
Mikael Persbrandt as Jakob Nyman (series 1–3), Ola's father and a widowed Swedish
plumber who develops a relationship with Jean •
Anne-Marie Duff as Erin Wiley (series 2–3), a drug addict and the absent mother of Maeve, Sean and Elsie •
James Purefoy as Remi Milburn (series 2; guest series 1), Otis's father and Jean's ex-husband, a therapist and sex addict who lives in America •
Rakhee Thakrar as Emily Sands (series 3; recurring series 1–2; guest series 4), an English teacher at Moordale Secondary School •
Jemima Kirke as Hope Haddon (series 3), the new headmistress at Moordale Secondary School and Michael Groff's replacement
Recurring •
Jim Howick as Colin Hendricks (series 1–3; guest series 4), a science teacher at Moordale Secondary School who conducts the Swing Band •
Samantha Spiro as Maureen Groff, the headmaster's wife and Adam's mother •
Hannah Waddingham as Sofia Marchetti (series 1–2 and 4; guest series 3), one of Jackson's mothers •
Sharon Duncan-Brewster as Roz Marchetti (series 1–2 and 4), Jackson's other mother •
DeObia Oparei as Abeo Effiong (series 1), Eric's concerned and protective father • Doreene Blackstock as Beatrice Effiong, Eric's supportive mother • Chris Jenks as Steve Morley (series 1–3), a student at Moordale Secondary School, who becomes Aimee's boyfriend •
Lisa Palfrey as Cynthia (series 1–3), the owner of the caravan park where Maeve lives •
Daniel Ings as Dan (series 1, 3–4), Joy's real father •
Joe Wilkinson as Jeffrey, Cynthia's husband •
Jojo Macari as Kyle (series 1; guest series 2–3), one of Aimee's ex-boyfriends •
Edward Bluemel as Sean Wiley (series 1 and 4), Maeve's absent older brother who raised her instead of their parents • Chinenye Ezeudu as Vivienne 'Viv' Odusanya (series 2–4), a girl who tutors Jackson and is a member of the quiz team •
George Robinson as Isaac Goodwin (series 2–4), a
disabled boy who lives on the same campsite as Maeve • George Somner as Joe Goodwin (series 2–4), Isaac's brother and carer who lives on Maeve's campsite • Conor Clarke McGrath as Connor Pearson (series 2–4), a student at Moordale Secondary School •
Sami Outalbali as Rahim Harrack (series 2–3), a French exchange student who shows an interest in Eric •
Lino Facioli as Dex Thompson (series 2–3), a member of the quiz team •
Mirren Mack as Florence (series 2), an
asexual student at Moordale Secondary School • George Georgiou as Yousef (series 2), the owner of the local shop and Rahim's uncle •
Armin Karima as Malek Amir (series 2–3), Olivia Hanan's boyfriend • Conor Donovan as Quentin (series 2–3), a member of the drama club and enemy of Mr Hendricks •
Jason Isaacs as Peter Groff (series 3), older brother of Michael Groff •
Indra Ové as Anna (series 3, guest series 4),
foster mother of Maeve's younger half-sister Elsie •
Dua Saleh as Cal Bowman (series 3–4), a
non-binary student at Moordale Secondary School who relocated from
Minneapolis • Robyn Holdaway as Layla (series 3), a non-binary student at Moordale Secondary School •
Dan Levy as Mr Molloy (series 4), a teacher in the study program Maeve attends in the United States •
Hannah Gadsby as Celia (series 4), a manager at the radio station where Jean works •
Thaddea Graham as Sarah "O" Owens (series 4), a rival sex therapist student at Cavendish College •
Anthony Lexa as Abbi Montgomery (series 4), a popular girl and the leader of Cavendish College's The Coven clique • Alexandra James as Aisha Green (series 4), a member of The Coven who is partially deaf • Felix Mufti as Roman Zardari (series 4), a member of The Coven and Abbi's boyfriend •
Reda Elazouar as Beau (series 4), Viv's love interest •
Lisa McGrillis as Joanna Franklin (series 4), Jean's sister •
Anna Francolini as Gloria Masters (series 4), a teacher at Cavendish College • Shak Benjamin as Adedayo (series 4), Eric's love interest from his church •
Bella Maclean as Jem (series 4), Adam's co-worker at the farm • Imani Yahshua as Tyrone (series 4), a friend of Maeve's in America •
Eshaan Akbar as Principal Lakhani (series 4), headteacher at Cavendish College
Guest •
Toby Williams as Tim (series 1–2), one of Jean's patients •
Lu Corfield as Sarah (series 1), a mother of three who befriends Maeve •
Anjana Vasan as an
anti-abortion activist (series 1) • Dominic Applewhite as Charlie (series 1), an anti-abortion activist •
T'Nia Miller as Maxine (series 2), the chair of the school board • Thomas Atkinson as Nick (series 2–3), Anwar's boyfriend •
Stephen Fry as himself (series 2), a quiz host •
Sindhu Vee as Mrs Hanan (series 2), Olivia's mother •
Susan Lynch as Tara Gibbs (series 2), Aimee's mother •
Jack Bandeira as Eli (series 2), a student at Mountview Military Institution • David Layde as Roland Matthews (series 3–4), Ruby's father who has
multiple sclerosis and is Jeffrey's friend •
Miles Jupp as an
obstetrician at Moordale community hospital •
Sophie Thompson as Carol Iglehart (series 3), Lily's mother and a nurse • Jerry Iwu as Oba (series 3), a gay photographer from
Nigeria • Reece Richards as Eugene (series 3), Viv's boyfriend •
Jack Gleeson as Dodgy Mo (series 4), a friend of Sean's •
Andi Osho as Nicky Bowman (series 4), Cal's mother •
Jodie Turner-Smith as God (series 4), an apparition that appears to Eric ==Episodes==