For England as a whole, Northampton was affected by the “Swinging Sixties,” a period in which a youth-driven revolution opposed societal norms in music, fashion, and art. Bands such as The Beatles and The Rolling Stones influenced musical tastes, while designers like Mary Quant reshaped youth fashion. Haddon's writing does not necessarily focus on the local culture but rather on factors from his early life.

Haddon’s mother was a homemaker, while his father was an architect. He has an older brother, Paul, and a younger sister, Charlotte.  His father’s work inspired his love of art, as Haddon would draw on the backs of his father’s spare plans. His father encouraged his creative behavior as he continued to supply his children with the spare plans. Haddon’s favorite subjects to sketch were "underseas panoramas" and "castle sieges." 

His parents also made him attend a boarding school, Uppingham School, which Haddon severely disliked. He was moved away from art at the school because his teachers believed he could earn A Levels and that pursuing art was a waste of time. Nonetheless, Haddon didn’t allow the boarding school to stifle his creativity and continued to pursue his love for art. He claims that a day without putting a small new thing into the world is a day wasted.

When Haddon entered higher education, he attended Merton College, Oxford, in 1981, where he received a B.A. in English. He later attended Edinburgh University in 1984, earning a Master of Science in English Literature. With this knowledge, Haddon went on to give several speeches on creative writing and literature at universities and festivals. His most recent speech was in September 2024 at a festival focused on his book of short stories, Dogs and Monsters.

As a child, Haddon read nonfiction books about science, chemistry, and archaeology. He was naturally a curious child, similar to Christopher Boone, and would read through the Origins of the Universe. He was extremely interested in becoming a paleontologist when he grew up. His early preference for nonfiction is ironic, given that he later became known for writing fiction.

Before becoming a novelist, Haddon worked as a cartoonist for several publications and created children’s books and television shows, proving that his creativity had not been smothered by boarding school. Examples of his earlier works include Gilbert’s Gobstopper, the Agent Z series, and Microsoap. Gilbert’s Gobstopper was Haddon’s first published novel and was geared toward a child audience, setting the tone for his future works.

Additionally, Haddon worked with individuals with mental and physical disabilities at an adult training center in North London and volunteered to assist a man with multiple sclerosis in Scotland. These experiences gave him insight into real-world issues and led to recurring themes of mental health and self-discovery in his writing. They also influenced novels such as The Curious Incident of the Dog in the Night-Time. Other famous works by Haddon include A Spot of Bother, The Red House, and The Porpoise.