The song was written by band members Zac Barnett, Dave Rublin, Matt Sanchez, and James Adam Shelley, along with producers Aaron Accetta and Shep Goodman.

[1] Dave Rubin spoke in a podcast of Songfacts where he disclosed that the song was being written when the Sandy Hook Elementary School shooting happened in 2012.

"[2] Zac Barnett told an interviewer for Blueprint Magazine, "Recently we have been experimenting with a lot of different instruments including banjo, mandolin, and various percussion toys.

Bill Lamb, writing for About.com, praised the song's "opening banjo lick" as "a perfect first hook," its "irrepressibly upbeat lyrics," and "a blend of key elements from across a wide range of current successful pop music."

[citation needed] In media, the song has been featured in television advertisements for: retail home improvement store Lowe's in the United States, which were aired during the Super Bowl,[14] automotive manufacturer Hyundai in the United Kingdom and France, an alcohol retailer in Australia and communications service provider Telecom New Zealand in New Zealand.

It appears in the movie trailer for the films Delivery Man, Yes Day, The Secret Life of Walter Mitty[17] in addition to the TV spots for St. Vincent.

[citation needed] A 2024 cover of the song, a poppunk version by Ivyvox, has been used in the Dutch film Verliefd op Bali made by movie director Johan Nijenhuis.

[19] The song was covered by Blaine Anderson (Darren Criss) and Sam Evans (Chord Overstreet) in the 2014 Glee episode "New New York".

American Authors performed the song while in Human Centipede position on season four premiere of The Eric Andre Show.

"Best Day of My Life" also appeared as a soundtrack in Konami video game Pro Evolution Soccer 2015 as the opening track.

"Best Day of My Life", was the official song of the 2017 Maltese Labour Party's General Election Campaign, entitled "L-aqwa żmien ta' pajjiżna."

"Best Day of My Life" was played at the conclusion of the 2015 Miss America pageant, during Kira Kazantsev's crowning moment.

It depicts a man engaging in various activities with a large furry monster, such as drinking in a bar called Sweet & Vicious in Nolita,[21] playing basketball, looking at the Brooklyn Bridge, getting matching tattoos, visiting a strip club, and going to a playground.

"[21] Common Sense Media reviewed the video for parents: "There's nothing iffy to worry about in the song's upbeat, clean lyrics about having a positive outlook on life and never giving up, but the official music video shows a man and his furry monster friend drinking in a bar, going to a strip club, and getting tattoos.