He was born in Hampstead, London. His father was a doctor and his mother a sculptor. He was the second of six children; he had three brothers and two sisters and two half-sisters. The family emigrated to New Zealand in 1946-7. He attended Rongotai College in Wellington. On leaving school, he joined the New Zealand Players (as a spear carrier and ASM), the only professional theatre company in New Zealand at the time, under the directorship of Richard Campion. In 1954 he returned to London to attend the Slade School of Art. After leaving the Slade, he went back into the theatre and joined Guilford Repertory Theatre Company as a stage manager.
In 1958 he moved to the Royal Court Theatre in Sloane Square, London, where he worked for the next three years. Subsequently he worked as a director, at Cheltenham Repertory Company and elsewhere, including as Assistant Director to Peter Ustinov in London and New York. He directed the first two cabarets at Peter Cook's Establishment Club and spent a year at the BBC working in the Tonight department. In 1964, he left the theatre and devoted himself to a new career as a cartoonist. At this time, with Barry Humphries, he invented the Barry McKenzie comic strip in Private Eye. Garland also worked for The Spectator and other journals. In 1966, he was appointed the first political cartoonist of The Daily Telegraph where he remained until 2011, with a short break from 1986 to1990 when he was one of the founding journalists of The Independent . He was political cartoonist on the New Statesman during the 1970s and worked for The Spectator for many years.
His son, Tim, whose mother was the painter Margaret Evans, was born in 1957. Garland married Harriet Crittall in 1964, their daughter, Emily was born in 1966; the marriage was dissolved in 1968. In 1969 he married Caroline Medawar, they had two sons: Alexander (1970), Theodore (1972), the marriage was dissolved in 1994. In 1995 he married Priscilla Roth. They live in Belsize Park, London.
In 2012, he was appointed Cartoonist of the 2012 London Olympics by the Mayor of London, Boris Johnson. In this position he did a series of drawings, woodcuts and paintings, published in the book: "Drawing the Games". Garland's work is represented in the British Museum, the Museum of London, and the Ashmolean Museum. He has exhibited woodcuts at the Fine Arts Society in Bond Street and his publications include (illustrated) Horatiius, by T.B. Macaulay (1977), an Indian Journal (1983); Twenty Years of Cartoons (1984); Travels With My Sketchbook (1987); Not Many Dead (1990); (illustrated )The Coma, by Alex Garland (2004) ; I Wish… (2007); Mommy, Daddy, Evan, Sage, by Eric McHenry (2011). Decorations: OBE 1998.
- "Birthdays". The Guardian. Guardian News & Media. 1 Sep 2014. p. 29.