According to Geldof, he wrote the song after reading a telex report at Georgia State University's campus radio station, WRAS, on the shooting spree of 16-year-old Brenda Ann Spencer, who fired at children in a school playground at Grover Cleveland Elementary School in San Diego, California on 29 January 1979, killing two adults and injuring eight children and one police officer. Spencer showed no remorse for her crime and her full explanation for her actions was "I don't like Mondays. This livens up the day". The song was first performed less than a month later. Geldof explained how he wrote the song:
I was doing a radio interview in Atlanta with Fingers and there was a telex machine beside me. I read it as it came out. Not liking Mondays as a reason for doing somebody in is a bit strange. I was thinking about it on the way back to the hotel and I just said 'Silicon chip inside her head had switched to overload'. I wrote that down. And the journalists interviewing her said, 'Tell me why?' It was such a senseless act. It was the perfect senseless act and this was the perfect senseless reason for doing it. So perhaps I wrote the perfect senseless song to illustrate it. It wasn't an attempt to exploit tragedy.
Geldof had originally intended the song as a B-side, but changed his mind after the song was successful with audiences on the Rats' US tour. Spencer's family tried unsuccessfully to prevent the single from being released in the United States. Despite being a major hit in the United Kingdom, it only reached #73 on the USBillboard Hot 100. The song was played regularly by album-oriented rock format radio stations in the United States throughout the 1980s, although radio stations in San Diego refrained from playing the track for some years in respect to local sensitivities about the shooting. The song became Number One in the UK single charts in July 1979. In the UK it won the Best Pop Song and Outstanding British Lyric categories at the Ivor Novello Awards. It was subsequently covered by Tori Amos on her 2001 album Strange Little Girls and later by G4 on their 2006 album Act Three.
At a concert in London in 1995, just before the tenth anniversary of Live Aid (during which Geldof himself performed the song in the Boomtown Rats' final major appearance), Bon Jovi covered the song after being joined on stage by Geldof at Wembley Stadium. This recorded performance features on Bon Jovi's live album One Wild Night Live 1985–2001, as well as on the bonus 2-CD edition of These Days. Bon Jovi were again joined by Geldof for a performance of the song at The O2 Arenaon 23 June 2010, the 10th night of their 12-night residency. Geldof himself performed an impromptu version of the song while hosting the Live 8 concert in London, on 2 July 2005.
In "20 Hours in America, Part II", the second episode of season 4 of The West Wing, the song (covered by Tori Amos) was featured during the aftermath of a fictional bombing at Kennison State University in Cedar Rapids, Iowa, the story behind the song having been told in the previous episode: "20 Hours in America, Part I".
The title of the song can be seen scrawled in graffiti on a set of lockers at the beginning of the 1985 film The Breakfast Club.
The song appeared in the television series House in the episode "Half-Wit". Dr. House (Hugh Laurie) played the piano introduction to the song for a patient (Dave Matthews), a musical savant with dystonia, who then repeated it perfectly (with House adding the distinctive hand claps between the last two phrases).
Tori Amos' cover of the song was also used in a major touring production of Romeo and Juliet by Headlong in a sequence many theatre critics commented on, where its refrain of 'Tell me why' spoke to the production's emphasis on coincidence and chance leading to the play's tragedy.
VH1 rated the song at #67 on its list of the top 100 one hit wonders of the '80s, despite the song being released in 1979 and the Boomtown Rats having several other hits in Great Britain and Ireland.
In 2006 while presenting the NME Awards, Russell Brand made the joke, "Really, it's no surprise he's (Geldof) such an expert on famine; he has after all been dining out on 'I Don't Like Mondays' for thirty years".