The song received positive reviews from critics, who praised the production, lyrics, and vocals, calling it a highlight on the album.

[4] The song has also reached number one in Sweden and in the top 20 in several countries including Australia, Canada, New Zealand and the United Kingdom, becoming Imagine Dragons' most successful single to date.

[5] "Radioactive" received two Grammy Awards nominations for Record of the Year and Best Rock Performance, winning the latter.

"In a 2021 interview, Reynolds revealed that, on looking back at the song after almost a decade, he had realized that its lyrics were actually about him not giving up hope after losing faith in Mormonism.

[14] Sheet music for "Radioactive" shows the key of B Dorian (a mode of F# minor or A major, in which B is used as the tonic), in 4/4 common time, and a tempo of 132bpm, with a chord progression of Bm-DSus2-A-E, and vocals spanning from E4 to B5.

[20] Our Vinyl stated that the "power of this song is outstanding with heavy drums and more of an electronic feel than the rest of the album and strong, impressive vocals from front-man Dan Reynolds which are reciprocated throughout the LP.

"[21] Jon Dolan of Rolling Stone was critical of the song, calling it "a dour moaner that sound[s] like Chris Martin trying to write an Eminem ballad about the end of the world.

"Radioactive" debuted at 96 on the Billboard Hot 100 after the release of Night Visions in September 2012 and remained at the lower ends of the chart for some time.

[28] "Radioactive" currently holds the record for the longest reign atop the Billboard Rock Airplay chart, with 24 weeks.

[29][30] In late 2023, for Alternative Airplay's 35th anniversary,[31] Billboard placed "Radioactive" at number eight on its ranking of the top 100 largest hits in the chart's history.

2 Song of the Summer according to Billboard and spent 87 weeks on the Billboard Hot 100, breaking the all-time chart longevity record, previously held by Jason Mraz's 2008 single "I'm Yours", and overtaken by the Weeknd's 2019 single "Blinding Lights", which spent 90 weeks on the Hot 100 as of the chart issue dated September 4, 2021.

[35] It has gone on to sell 8,234,360 digital copies in the nation as of September 2017,[36] and was certified Diamond by the Recording Industry Association of America (RIAA).

[37] The song has reached number one in Sweden and in the top twenty of several countries such as Australia, Canada, New Zealand as well as several parts of Europe.

[38] Directed by Syndrome and featuring puppeteers from Puppet Heap, the video revolves around a mysterious female drifter (played by actress Alexandra Daddario) on a quest to save her friends in Imagine Dragons from the perils of a sinister, underground puppet-fighting ring led by actor Lou Diamond Phillips.

The first televised performance of "Radioactive" was on the September 4, 2012, airing of ABC late-night talk show Jimmy Kimmel Live!.

"Weird Al" Yankovic recorded a parody version entitled "Inactive" for his 2014 album Mandatory Fun.

[47] Lady Antebellum covered the song live backstage on their Take Me Downtown Tour and put the video on their YouTube channel.

Independent American singer Madilyn Bailey recorded an acoustic cover that reached number 36 on SNEP, the official French singles chart, in June 2015.

The Night Visions track was remixed by the band, featuring guest vocals from American rapper Kendrick Lamar.

The remix, while retaining most of the original track from Continued Silence, was recorded by the band and Kendrick Lamar for release as a single.

"Radioactive" was first performed by Imagine Dragons and Kendrick Lamar at the 56th Annual Grammy Awards, held at the Staples Center, Los Angeles on January 26, 2014.