[4][5] Steadman took his first job at 16 as a RADAR Operator at the De Havilland aircraft factory in the border town of Broughton near Chester but only remained for nine months, finding factory life repetitive and dull, and becoming fed up with fellow employees, citing persistent cruel practical jokes ("They were always putting stuff in your tea"); however, whilst there he became skilled in technical drawing, thus sowing the seeds of his future career.

Steadman has expressed regret at selling the original illustrations for Fear and Loathing in Las Vegas at the advice of his agent to Rolling Stone founder Jann Wenner for the sum of $75, a fraction of their later value.

As well as writing and illustrating his own books and Thompson's, Steadman has worked with writers including Ted Hughes, Adrian Mitchell and Brian Patten, and also illustrated editions of Alice in Wonderland, Treasure Island, Animal Farm, the English translation of Flann O'Brien's Gaelic-language classic The Poor Mouth, and most recently, Fahrenheit 451.

Steadman has drawn album covers for numerous music artists, including the Who, Exodus, Frank Zappa and Ambrosia, and the lead banner for the gonzo journalism website GonzoToday.com.

Steadman has contributed to the BirdLife International's Preventing Extinctions programme with an image of critically endangered northern bald ibis.

[13] In 2020, Steadman created the artwork for the documentary film Freak Power: The Ballot or the Bomb which follows journalist Hunter S. Thompson and his 1970 campaign for sheriff of Pitkin County, Colorado.

Flying Dog and the American Civil Liberties Union sued the state of Colorado while the displayed motto was changed to "Good Beer No Censorship."

In 2001, the Colorado Supreme Court entered final judgment in favor of Flying Dog, based on the First Amendment to the United States Constitution, (freedom of speech).

In 2015, the 6th Circuit Federal Court of Appeals struck down the ban on first amendment grounds and recommended civil damages against the state of Michigan.

The Portman Group, a third-party organization which evaluates alcohol-related marketing in the UK, has accepted the complaint's allegation that the artwork "could be seen as encouraging drunkenness", particularly among minors, and has issued an advisory.

[20] In 2021, Flying Dog sued the North Carolina Alcoholic Beverage Control Commission for violation of free speech provisions after the NC ABC rejected the label for the brewery's "Freezin' Season" beer as "inappropriate".

[21] In 1980, Steadman wrote a 57-second song "Sweetest Love (Lament after a Broken Sashcord on a Theme by John Donne)" for an album he was illustrating, Miniatures: A Sequence of Fifty-One Tiny Masterpieces (edited by Morgan Fisher), on Pipe Records.

A major documentary about Steadman's career, For No Good Reason, directed by Charlie Paul, played at the 2013 Toronto International Film Festival in the "Mavericks" programme.