2013–2015: Career beginning and Britain's Got Talent

On 15 August 2013, Scott won the talent competition Mail's Star Search, organised by Hull Daily Mail.^[3][4] He then joined a Maroon 5 tribute band, Maroon 4, and toured around the United Kingdom.^[5] In 2014 he formed the electronic duo, The Experiment with John McIntyre.^[6] The debut single, "Girl (You're Beautiful)", was released on 14 June.^[7] The duo performed the song on Good Morning Britain and BBC Look North, but after, broke up.^{[8][9] [10]}

On 11 April 2015, Scott's audition for the ninth series of Britain's Got Talent was broadcast on ITV. Just before his audition, his sister Jade also auditioned but was stopped early on both of her songs by Simon Cowell. Jade received four "No" votes from David Walliams, Alesha Dixon, Amanda Holden and Simon Cowell.

Despite obvious nerves at seeing his sister get rejected, Calum performed a cover of Robyn's "Dancing on My Own", which he had heard Kings of Leon performing on BBC Radio 1's Live Lounge in 2013. Following a standing ovation from the judging panel, Cowell pressed the Golden Buzzer giving Scott an automatic place in the live shows. Explaining his decision to send Scott straight to the semi-finals, Cowell said:

"I've never ever in all the years I've done this show heard a guy with the talent you've got. Seriously. And the version was sensational, and that shows to me that actually, you're more than a singer, you're an artist, and that's why you got that (the buzzer)."

After this audition, Scott received support from stars such as Little Mix and Ashton Kutcher.^[11]

Following his appearance on the show's first episode, his Twitter followers jumped from 400 to over 25,000.^[12] The video of his audition has been viewed over 378 million times on YouTube. In the semi-final on 29 May, Scott performed "We Don't Have to Take Our Clothes Off" by Jermaine Stewart. Walliams commented "You really sound like a recording artist", whilst Alesha Dixon suggested that he could have "success around the world". He won the semi-final with 25.6% of the vote, sending him straight through to the final. In the final on 31 May, Scott performed "Diamonds" by Rihanna and finished sixth out of 12 contestants with 8.2% of the vote. After Britain's Got Talent, Scott embarked on a series of shows around the United Kingdom, including Viking FM Future Star Awards, Flamingo Land Resort Fair, Westwood Cross Shopping Centre's tenth anniversary, Gibraltar Summer Nights, Hull Daily Mail's Star and Dartford Festival.^{[13][14][15][16][17][18]}

2016–2018: Only Human

Scott at the Tabernacle, United Kingdom, in 2016

Scott released his cover of "Dancing on My Own" independently on 15 April 2016. It became a sleeper hit, first hitting number 40 in the charts in May and climbing into the top 40 despite little radio airplay apart from on West Hull FM. It was then added to Radio 2's "C List" and reached number two on the UK Singles Chart on 5 August. In August 2016, it was certified platinum in the UK, having sold over 600,000 copies.^[19] Scott announced on Twitter on 24 May that he had inked a record deal with Capitol Records, where he was signed by A&R Executive Alex Wilhelm.^[20][21] Scott performed the song at television shows BBC Look North, Lorraine, Weekend, Late Night with Seth Meyers and Brazilian show Encontro com Fátima Bernardes.^[22] He also promoted the song on several radio stations, including BBC Radio Humberside, Viking FM, Radio Gibraltar, BFBS Radio and Gibraltar Broadcasting Corporation.^[23][24][25] On 16 September, he released the promotional single "Transformar" with Brazilian recording artist Ivete Sangalo as the official song of the 2016 Summer Paralympics in Rio de Janeiro; they performed the song at the closing ceremony on 18 September.^[26][27] It was revealed in September 2016 that "Dancing on My Own" was the most downloaded song of the summer in the UK.^[28] In autumn 2022, "Dancing On My Own" had a sudden resurgence in popularity due to the Philadelphia Phillies players and fans embracing the dance mix version of the song during the team's run to the 2022 World Series.

In 2017, he toured the US and released the single "You Are the Reason". Also in 2017, he began working on his debut album, Only Human, which was released on 9 March 2018. A new version of "You Are the Reason" was released ahead of the album in early 2018 as a collaboration with Leona Lewis, and was performed by the two on The One Show in February 2018. In May, Scott released "What I Miss Most" as the fourth single from Only Human.

In October 2018, Scott released a new single titled "No Matter What". Upon release, Scott said:

"'No Matter What' is without question the most personal song I have ever written and the one I am most proud of. It's a song born from loneliness, acceptance and the heartbreaking but liberating tale of my coming out experience. What I love about this song is that it isn't just limited to a story of sexual identity, but about the relationship between parent and child and acceptance as a whole. This song didn't make my debut album because I simply wasn't ready at that time to give it to the world."^[29]

2019–present: Bridges

In September 2020, Scott partnered with American watch company Bulova on the development of a music documentary series titled Minutes with Calum, which explores the creative process behind his upcoming second album through the lens of Bulova.^[30]

In March 2021, Scott digitally released his first EP, titled Only Acoustic, which featured acoustic renditions of songs from his debut album. The following month, he released two more EPs; Only Collabs and Only Love. On 11 June 2021, Scott released the single "Biblical",^[31] the first song from his upcoming second album. He released the second song titled "Rise"^[32] on 1 October 2021, and the third song titled "If You Ever Change Your Mind"^[33] on 4 February 2022. On 29 April 2022, Scott announced that his second album, Bridges, would be released on 17 June 2022.^[34] On the same day, he released the fourth song, "Heaven", from the album.^[35] In July 2021, Scott collaborated with Belgian artist Lost Frequencies singing on a song titled "Where Are You Now", which was released on 30 July 2021. The song became a big hit over the next several months, charting on many streaming platforms in many countries.^[36] In early February 2022, the song reached the top 10 of the UK Singles Chart, becoming Scott's second song to reach the UK top 10.^[37] In November 2021, Scott collaborated with Brazilian recording artist Bryan Behr, singing on the song "Da Primeira Vez (From the First Time)". Scott sang in both English and Portuguese.^[38] Also in November 2021, he collaborated with British singer Jasmine Thompson on a song titled "Love Is Just a Word".^[39]

In February 2023, Scott collaborated with GRAMMY-nominated producer, DJ, and record label executive, Jax Jones on a song titled "Whistle" which was released on 10 February 2023. Scott has recently performed the track live at the BAFTA Film Awards. Scott performed live with Take That on 7 May 2023 at the Coronation Concert in the grounds of Windsor Castle.^[40] On 18 August 2023, Scott released the single "At Your Worst",^[41] Upon the release of the song, Scott shared, "This could be a song reassuring someone that you'll love them no matter what, but it's also a song to yourself: a reminder that you should love yourself at your worst because self-love is the most important. The sound on this one feels nostalgic and retro to me — kind of takes me back to my Sega Mega Drive. I’m excited to share new music with my fans and show everyone what I’ve been working on!"^[42] which debuted at number 20 on the UK Singles Downloads Chart a week later.^[43]