Born in 1971 to an English father and Irish mother (whose grandfather was a seanchaí), he attended St. Martins School in Northwood before moving on to Merchant Taylors' School. He studied English at the University of London, and went on to teach the subject for seven years, becoming head of the English department at St Gregory's Roman Catholic School in London. He eventually left teaching to write his first novel, The Gates of Rome. He is married with three children and lives in Hertfordshire, England.
Iggulden's debut book was The Gates of Rome, the first in a four-part series entitled Emperor. The series is based around the life of Julius Caesar, from childhood (The Gates of Rome) to his eventual betrayal and death (The Gods of War). The film option has been sold to Spitfire Productions (an Intermedia company).
The author has indicated that in the future he will write a fifth book that deals with the events after the end of The Gods of War. He mentions it on his website 'projects'.
After completing the fourth book in the Emperor series, Iggulden began research for his next series of books, the Conqueror series, based on the life of Mongol warlords Genghis ,Ogedai and Kublai Khan. His first book was available from 2007. Bones of the Hills , the third in the series, was released on 1 September 2008. In September 2010 'Empire of Silver' will be released which revolves around the life of Genghis Khan's son, Ogedei. Iggulden has confirmed on his official website that he will be writing two more books after "Empire of Silver" on Kublai Khan and then one more Emperor book on Augustus.
Iggulden co-wrote a book with his brother Hal, The Dangerous Book for Boys. It covers around eighty topics, from building a soapbox racer and tying knots, to learning about famous battles and how to make potassium aluminium sulphate crystals. It was released in the UK in June 2006, reprinted a month later and was voted British Book of the Year at the Galaxy British Book Awards.
On September 2009 he wrote a children's book Tollins: Explosive Tales for Children through Harper Collins. Iggulden has since written three stories to accompany the story of the Tollins.
In March 2006, Iggulden released a novelette entitled Blackwater, part of the Quick Reads initiative of World Book Day 2006. Being a thriller, Blackwater was a change in genre for Iggulden who had mainly written historical fiction.