Condell left school at 16, his first job being a dish-washer in the revolving restaurant on top of the Post Office Tower, now known as the BT Tower in London, for five shillings an hour. He became a vegetarian in 1976 after watching a deer being butchered. Condell did a number of jobs including six years of logging in Canada.

Condell performed alternative comedy shows during the 1980s and 1990s in the United Kingdom. His first performance on stage was at the age of 32 in a comedy Sketch called Mountbatten’s Plimsoll. He also wrote poetry and appeared in the Poetry Olympics at the Young Vic Theatre in 1982, which led to a job writing weekly poems for the Time Out magazine. Condell was described at the time as "a manic gimlet-eyed, crop-haired poet" in Drama: The Quarterly Theatre Review book.

From 1991 to 1994 Condell was a regular panellist on BBC Radio 1's "Loose Talk." During the mid-1990s, he was performing over 200 times a year. Due to the late nights and regular travelling he decided to start writing for other comedians, while still doing the occasional performance. In 1991 he performed comedy sketches at Duke of York's Theatre, which were released onto VHS as Barf Bites Back! (1991).

Condell's 1996 play Barry Sorts It Out was given a negative review in the Financial Times, which described it as "a sordid East End comedy" which "repeats ad nauseam the same gag." The reviewer concluded that it is "a play with all the bite of a set of joke-shop fangs."

Condell has been resolute and outspoken in his opposition to the development of Park51, near the site of 11 September 2001 World Trade Center attack, in lower Manhattan. On 4 June 2010, he released a video titled "No Mosque at Ground Zero", in which he said that it was representative of Islamic triumphalism and that the United States would soon be on the verge of Islamization and have its freedoms trimmed, as Europe has. The video has attracted 6 million views since it was uploaded. Speaking on why he believes the Mosque is offensive, Pat Condell stated:

His 2006 stand-up show Faith Hope and Sanity, subtitled "A Few Jokes About Religion Before It Kills Us All," was a platform for his comedy and atheist beliefs. "This is the first time I’ve set out to write a show in order to say something, rather than just as a vehicle for stand-up" he said of the show. He performed the show at London’s Etcetera Theatre. Chortle gave Condell's 2006 show a negative review, noting that Condell is covering familiar territory but "is not quite up to the job," and observing that Condell's material was delivered "with very little variation in pace or tone, ... with the feel of a lecture" and "no structure, no building up to a passionate, climactic conclusion, no ebb and flow of storytelling." Chortle concluded that "Condell is still going through the motions."

In 2007 he was criticised by Christian author Dinesh D'Souza on AOL News, who said "If the Televangelists are guilty of producing some simple-minded, self-righteous Christians, then the atheist authors are guilty of producing self-congratulatory buffoons like Condell." The book Raising Freethinkers: A Practical Guide for Parenting Beyond Belief, describes Condell as "breathtakingly intelligent, articulate, uncompromising, and funny". The New York Times Magazine described Condell as a "smug atheist".

Condell's video Welcome to Saudi Britain was removed by YouTube early in October 2008, but reinstated shortly after. In it Condell criticises Britain's sanctioning of a Sharia court, and refers to the entire country of Saudi Arabia as "mentally ill" for its abuse of women.

Additionally, Condell cast some doubt over the funding of the community centre, and claimed that Islam would have been banned in the civilised world if it wasn't for the fact it was a religion. He compared the system of Sharia and the Muslims who endorse it to Nazi Germany. The video was among the top 10 most discussed YouTube videos of 2010.

Condell had posted more than 100 video monologues on various video sites as of August 2011, which together had notched up over 35 million hits, and his videos have been translated and subtitled into 14 languages on the dotSUB collaborative platform. In September 2009, he was one of the top ten most subscribed users on YouTube in the United Kingdom and the most subscribed to Comedian of all time in the UK. Eight of his videos are in the top hundred most commented on videos in the UK. Most of his YouTube videos chastise Islam and Western appeasement of Islam. His videos have caused Condell to receive hundreds of death threats but also a significant amount of support.

Condell then accused Cohen of being "motivated by his own narrow personal and political agenda which has nothing to do with [Condell] or the video clip". The video was initially sent to them by fellow Peace and Justice Commissioner Jonathan Wornick, who said it "tries to expose intolerance in the Muslim world", such as "the intolerance of radical Islamists who say if you insult Allah, you should have your head cut off". Condell said that its popularity proves "there is an enthusiastic audience for comedy ideas and opinions which are routinely censored out of existence in the UK’s mainstream media, thanks to misguided political correctness".