It was written by Sean, Josh Alexander, Billy Steinberg, Jeremy Skaller, Rob Larow, Khaled Rohaim and Israel Cruz.

"What Happened to Us" was leaked online in October 2010, and was released on 10 March 2011, as the third single from Mauboy's second studio album, Get 'Em Girls (2010).

"What Happened to Us" was written by Josh Alexander, Billy Steinberg, Jeremy Skaller, Rob Larow, Khaled Rohaim, Israel Cruz and Jay Sean.

[5] Majhid Heath from ABC Online Indigenous called the song a "Jordin Sparks-esque duet", and wrote that it "has a nice innocence to it that rings true to the experience of losing a first love.

"[6] Chris Urankar from Nine to Five wrote that it as a "mid-tempo duet ballad" which signifies Mauboy's strength as a global player.

[13] The video begins showing Mauboy who appears to be sitting on a yellow antique couch in a mansion, wearing a purple dress.

As the video progresses, scenes of memories are displayed of Mauboy and her love interest, played by Sean, spending time there previously.

[13] David Lim of Feed Limmy wrote that the video is "easily the best thing our R&B princess has committed to film – ever" and praised the "mansion and wondrous interior décor".