Written by the band alongside Vincent Pontare, the song contains elements from Marlena Shaw's 1967 recording of "Waiting for Charlie to Come Home", penned by Bob Hilliard and Burt Bacharach.

"Heart Is Full" received mixed reviews from critics; some applauded the use of the sample combined with the hip hop beat, while others felt it was uninspired as a whole.

"Heart Is Full" was written by Miike Snow's three members, Christian Karlsson, Pontus Winnberg and Andrew Wyatt, in collaboration with Vincent Pontare, for the band's third studio album, iii (2016).

[2] Bob Hilliard and Burt Bacharach received writing credits due to the inclusion of the "Waiting for Charlie to Come Home" sample, as performed by Marlena Shaw.

[5] Wyatt explained to Rolling Stone that the song is a "total departure" from the band's previous albums and asserted, "I think we challenged ourselves and we still ended up making stuff that's good.

"[1] The band debuted the full track on Zane Lowe's radio show World Record on Apple Music's station Beats 1 on 29 October 2015.

[13][14][15] It contains elements of Marlena Shaw's 1967 rendition of "Waiting for Charlie to Come Home"[9] and instrumentation based on drums,[16] horn,[12] percussion,[10] synths[17] and Wurlitzer electric piano.

[10][18] Describing the record, Wyatt stated, "The thing I like about 'Heart Is Full' is that it's kind of like a 60s garage music song like Troggs or something over a 90s hip hop beat.

[16] Similarly, Alex Gale of Billboard wrote that is sounds "like a DJ Premier remix, with a chopped-up soul sample and huge drums giving Wyatt's Auto-Tuned pop-rock hook a muscular jolt".

Michelle Geslani, writing for Consequence of Sound, viewed the single as a "bold comeback track" and complimented its "rich, soul samples, thundering beats, and larger-than-life melodies that'll make you forget Miike Snow was ever gone to begin with".

[17][21] Ben Hogwood of musicOMH called "Heart Is Full" an "excellent" song, praising it for combining the Shaw sample with "broad hip hop beats".

"[28] An official remix of "Heart Is Full" featuring American hip hop duo Run the Jewels, consisting of Killer Mike and El-P, premiered on 19 November 2015 on The Fader.

[16][31] He felt that it could end up lacking progressive qualities, but said that Mike "found this riff through the song that was so perfect that you can't even classify it in a genre or a year".

[32] Wyatt explained he "couldn't stop smiling" when he first heard Mike's verse as the rapper had "found that flow, the rhythm to his lines that was undeniable".

[33] Hudson, writing for Exclaim!, said that while the arrangement is the same as the original version, Mike and El-P "drop by for a couple of full-throttle verses, and they offer a rather twisted take on romance".

[34] Spin's James Grebey wrote that the duo "dominat[e] the booming beat with an impact that lingers well after their verses end",[35] and Geslani of Consequence of Sound said they "effectively elevate the whole thing to entirely new levels of hip-hop/soul/pop bliss".