Following its usage on American reality TV show So You Think You Can Dance, the track gained attention from singer Christina Aguilera, who wanted to collaborate with A Great Big World on the song.

"Say Something" was originally released on February 8, 2011, on band member Ian Axel's solo album This Is the New Year with the song featuring harmonies by guest vocalist Jenny Owen Youngs, but the track went largely unnoticed until it received attention after being used on the TV series So You Think You Can Dance on season 10's semi final episode contemporary dance routine by the eventual champion Amy Yakima.

[1] About approaching the duo to re-record the track, Aguilera said, "Somebody sent me the song (...) and it's just the most simplest song that doesn't have to fit a formula to be heard and to be appreciated, so I just heard it and I've never done anything like this before and I was just like, 'You know', I just started to hear a harmony part over it and I was like, 'get in touch with these guys and see if they wanna get in the studio and sit behind the piano and just vibe together and see what happens...' and we did, and they're so humble, so sweet, so down to earth, and I'm all about that and supporting that, and we came together so organically and it was fun.

[4] The lyrics evoke the emotion felt when choosing to leave a failed relationship even though love still remains, imploring the lover say something because the singer is giving up on them.

"[1] Lewis Corner of Digital Spy noted that with its "stripped-down melody and emotive lyrics", the song becomes the antithesis of the club-thumping blow-outs radio currently prefers.

Rick Florino of Artist Direct gave the song five out of five stars, calling it "Oscar-worthy", with "a cinematic heft to the track that makes it utterly vivid and vibrant."

[11] Lewis Corner of Digital Spy praised Aguilera for "reminding us why she always sounds infinitely better when heading up a ballad", calling it "a beautifully simplistic ode to heartache that evidently connects.

"[14] Sam Lansky of Idolator wrote that the song "was already pretty heartrending, but Aguilera's vocals provide some lovely support and additional pathos; it's a relief to hear that she enriches, rather than overwhelms, the track.

"[7] Bradley Stern of MuuMuse praised the "slow, sad piano melody", the "mournful strings," calling it "a haunting production – made even better by the Stripped diva, proving once again that less is often more."

Stern also praised Aguilera for showing a simple side of her voice, writing that she "doesn't even have her own verse or chorus – she resigns to delivering subtle, yet effective, backing vocals for the entirety of the re-recording.

Brad Shoup of Pitchfork panned the song, writing "A compelling portrait of a sociopath who knows he’s about to utterly dominate yet another game of emotional chicken, “Say Something” is the sound of someone who only knows how to fall in love with Sigur Rós videos.

It’s goosed by the name, if not the presence, of La Aguilera; she’s so tiny here, it’s as if she’s echoing her lover’s words on the drive home, cratered by the idea that she gave herself for so long to something so monstrous.

[38] A music video, directed by Christopher Sims, was already shot on November 8, 2013, with Aguilera posting a picture of her standing next to a piano, where the duo is playing the track, to her Twitter, Facebook and Instagram page.

[42] The video features Aguilera in a simple black dress and natural make-up, reminiscent of her "Beautiful" days, according to MTV's Natasha Chandel.

Meanwhile, various tear-inducing images accompany the majestic track, often in slow motion – most strikingly, an older man climbing into a hospital bed with his peaceful female counterpart and emitting a silent shout.

"[46] Bradley Stern of MuuMuse agreed, writing that, "Armed with nothing else but a piano and an old bed frame by her side, the 'Lotus' legend bares her soul and gives you pure Stripped-era vulnerability, conjuring the simple-yet-effective one-take video for 'The Voice Within.'

Like, hand us a bucket, because we are ugly-crying from our eyes, noses, mouths, ears, and at least 17 other places where tear ducts biologically shouldn't be located.”[48] Mike Wass of Idolator also praised the video, writing that, "In keeping with the song's soft and subtle tone, the visual is understated and classy.

"[49] Natasha Chandel of MTV praised "a rare moment, when Xtina breaks down on camera as the hook, 'Say something, I'm giving up on you' crescendos, exposing a tender side to the singer that we haven't seen since her album Stripped.

The performance consisted of a piano, some strings and a keyboard for instrumentation, while Aguilera "reining in her voice's natural power", according to Billboard's Jason Lipshutz.

[1] The performance was lauded by critics and other artists, such as OneRepublic, Christina Perri, Ingrid Michaelson, Cee Lo Green and Carson Daly.

"[53] Bradley Stern of MuuMuse called the performance "perfect", writing that, "Christina keeps it as stripped as the studio version, allowing her naturally beautiful vocals to sound a whole lot more vulnerable than usual.

[55] With her hair in a braid and wearing a muted black dress, Aguilera sang an original verse midway through the performance, which included a string section and a fairly bare stage.

With A Great Big World's Chad King manning the keyboard, the group's Ian Axel sat at the grand piano and stamped his feet furiously as 'Say Something' approached its emotional climax," according to Billboard's Jason Lipshutz.

[56] Lindsay Dreyer of Wetpaint wrote that "Taking her rightful place center stage in a floor-length black dress and braided updo, the 32-year-old pop diva harmonized perfectly with the group's lead singer Ian Axel, who worked the piano with passion and poise.

Xtina's rich yet breathy tone offered just the right amount of strength and vulnerability — a side of Christina we haven't seen in a really long time."

Dreyer finished the review stating, "If tonight's AMA performance is any indication, Christina is on the brink of a major music comeback — and we can't wait!.

[60] The band (sans Aguilera) sang the song on the September 6 episode of Last Week Tonight in a duet with comedian John Oliver to mourn the loss of the Russian space geckos.

[63] American pop duo Alex & Sierra performed the song twice on third season of The X Factor (U.S.), where they were contestants and eventually won the show.

[67] Series creator and head judge Simon Cowell, who mentored the group, claimed that the duo success is proof that the show is still capable of turning small-town kids into bankable stars.

On January 19, 2014, The Voice of the Philippines coaches Sarah Geronimo and Bamboo performed their own rendition of the song on ABS-CBN's Sunday variety show ASAP 19.