In 2008, lead singer Dan Reynolds met Drummer Andrew Tolman at Brigham Young University where they were both students. Reynolds and Tolman added Andrew Beck, Dave Lemke, and Aurora Florence to play guitar, bass, and piano respectively for their band. Their name is an anagram for a phrase only known to members of the group, that Reynolds stated each member approved of. The five-piece released an extended play titled Speak to Me that same year. Beck and Florence would also depart from the band's lineup that year. In 2009, Tolman recruited longtime high school friend Wayne Sermon, who had graduated from Berklee College of Music to play guitar. Tolman later recruited his wife, Brittany Tolman, to sing backup and play keys, and the band began to play shows together again. Lemke left the band later on, leading Sermon to recruit another Berklee music student, Ben McKee, to join the band as their Bassist and complete the lineup. The band garnered a large following in their hometown of Provo, Utah, before the members moved to Las Vegas, the hometown of Dan Reynolds, where the band recorded and released their first three EPs.

They got their first big break when Train's frontman Pat Monahan fell sick just prior to the Bite of Las Vegas Festival 2009. Imagine Dragons were called to fill in and performed to a crowd of more than 26,000 people. Local accolades including "Best CD of 2011" (Vegas SEVEN), "Best Local Indie Band 2010" (Las Vegas Weekly), "Las Vegas' Newest Must See Live Act" (Las Vegas CityLife), Vegas Music Summit Headliner 2010, and more sent the band on a positive trajectory. In November 2011 they signed with Interscope Records and began working with English Grammy winning Producer Alex da Kid. Eventually the Tolmans would leave the group and Daniel Platzman would be recruited in August 2011 by invitation from Ben McKee, prior to the signing of the band's label deal in November 2011, alongside keyboardist Theresa Flaminio.

The band released EPs titled Imagine Dragons and Hell and Silence in 2010, both recorded at Battle Born Studios, in Las Vegas. They returned to the studio in 2011. The third EP, It's Time, was made before they signed a record deal.

Imagine Dragons has performed "It's Time" live on The Tonight Show with Jay Leno (2012) and Jimmy Kimmel Live! (2012) and Late Night with Jimmy Fallon (2012), and Conan (2013). They performed "Radioactive" live on Jimmy Kimmel Live! (2012), The Late Show with David Letterman (2013), The Tonight Show with Jay Leno (2013), Late Night with Jimmy Fallon (2013), and the MTV Europe Music Awards (2013). They also performed on Good Morning America (2013, 2015). The band performed an exclusive show for the sixth-season finale of the TV series Live from the Artists Den (2013). The band also performed at the 2013 American Music Awards, MTV Europe Music Awards (2013), Grammy Awards (2014), on Saturday Night Live (2014), at the Billboard Music Awards (2014), and the MuchMusic Video Awards (2014). They also headlined the MLB's Target All-Star Concert (2014) and the inaugural Made In America Music Festival Los Angeles. Imagine Dragons performed a version of "Revolution" at The Night That Changed America: A Grammy Salute to The Beatles (2014).

On October 24, 2013, Imagine Dragons guest-starred on an episode of truTV's Impractical Jokers, where losers Joe and Sal had to perform an opening act as "Señora Lanza" at a packed concert in Nikon at Jones Beach Theater. Band members join Murr and Q on the hijinks. The band has performed I Bet My Life at the 2014 American Music Awards, and The Ellen DeGeneres Show (2015). They have also performed "Shots" on The Tonight Show Starring Jimmy Fallon (2015), Jimmy Kimmel Live! (2015), and The Ellen DeGeneres Show (2015).

In 2013, along with the family of Tyler Robinson, Imagine Dragons started a charity called the Tyler Robinson Foundation, helping young people battling cancer. Beginning in 2014, the first annual Tyler Robinson Foundation Gala was held in Las Vegas. Imagine Dragons performed for "Playing It Forward" (S1 E2) to raise $100k for school music programs. In 2013, the band partnered with mtvU to help choose four Fulbright-mtvU Fellowship recipients. In 2013, Imagine Dragons partnered with Do the Write Thing: National Campaign to Stop Violence for a fundraising event. Imagine Dragons performed as part of Amnesty International's "Bringing Human Rights Home" concert in Brooklyn on February 5, 2014. In 2015, Imagine Dragons released the track "I Was Me" for the One4 project with all proceeds going to the UN Refugee Agency to support fleeing refugees, particularly in the Middle East. Imagine Dragons also released cover track "I Love You All The Time" to benefit the victims of the terrorist attacks in Paris. In 2017 the band helped organize the LoveLoud Fest to benefit LGBTQ organizations.

Imagine Dragons appeared on the first episode of the 2015 series The Muppets, to perform part of the song "Roots". They returned twice to The Ellen DeGeneres Show in 2017: the first time they performed "Believer", and the second time they performed "Thunder". They also performed the song on The Tonight Show Starring Jimmy Fallon.

On September 27, 2016, Imagine Dragons began teasing their third studio album with a tweet simply saying "studio". The band continued posting cryptic messages on their Twitter account for the next four months. On January 28, 2017, the band started posting a series of videos teasing the album's first single. The time-lapse videos featured lead singer Dan Reynolds drawing surreal images on a drawing pad. Morse code was hidden in the videos and translated to "objects of same color". On February 1, 2017, Imagine Dragons released "Believer" as the lead single for their next album. "Believer" was used as part of the Super Bowl ad for the Nintendo Switch.

The band collaborated with Khalid at the 2017 American Music Awards. They also performed "Believer" and "Thunder" at the New Years Eve party 2018 in New Orleans, which was broadcast live on Dick Clark's New Year's Rockin' Eve.

On February 14, 2018, Imagine Dragons announced a new single titled "Next to Me" on Twitter. The song was released as part of a re-issue of Evolve on February 21, 2018.

Inspired greatly by the band's travels on both their previous tours and the Night Visions Tour, the album explored world culture as a musical item and overall motif in the album. Dan Reynolds told New Orleans-based newspaper The Times-Picayune that there was "a lot of inspiration to be drawn from [the world tour]. You kind of realize that you’re a lot smaller than you think". In addition, Reynolds stated to music magazine Rolling Stone that the next album will be "different" from Night Visions, and that the band intends the album to be "stripped back quite a bit". He added that "we embraced a lot of hip-hop influences with Night Visions, but I think the next record will be more rock-driven. It’s too early to say, but there is some weird stuff going on in these songs".