Born in Victoria, he moved with his parents to Queensland as a child. The family ran the Queensland Reptile and Fauna Park, a small reptile park, which Steve became involved in running. When he was older, he became a crocodile trapper, removing crocodiles from near populated areas, performing the service for free with the quid pro quo that he kept them for the park.
In 1991, he took over the running of the park, now renamed the "Australia Zoo", and in 1992 met (at the park) and married Terri. The footage, shot by John Stainton, of their crocodile-trapping honeymoon became the first episode of The Crocodile Hunter, which became wildly successful in America.
In 2002, their first feature film, The Crocodile Hunter: Collision Course, was released. In 2003, Irwin was reportedly in line to host a chat show on Australian network television.
The Irwins have two children: a daughter, Bindi Sue Irwin (born 24 July 1998), and a son, Robert Clarence Irwin (born 1 December 2003).
Controversy arose when, on 2 January 2004, Irwin, in a public show, carried his infant son in one arm while feeding a dead chicken carcass to a crocodile with the other hand. He then set the child down on the ground near a pond with a crocodile in it. Child welfare and animal rights groups critized his actions as irresponsible and tantamount to child abuse, although Irwin was not charged criminally. Irwin stated that the danger to the child was only a perceived danger and that he was in complete control of the situation. Irwin's defenders pointed to his several decades of "hands on" experience and direct interaction with crocodiles, his well-known love for his children, and his respect for his role as a father. His wife Terri commented that the child was in no more real danger than a child being taught to swim would be.