Fallon began writing songs for what would become Painkillers before The Gaslight Anthem's 2014 release, Get Hurt, thinking there would be more time off before Get Hurt. He wrote new material and had some from another band of his, Molly and the Zombies, to use for Painkillers already. When the Get Hurt project started, Fallon put the new songs aside to focus on The Gaslight Anthem, realizing that the new songs he initially thought could be The Gaslight Anthem songs would not fit well with the direction the band was going with for Get Hurt. The band knew there would be a hiatus before it was made public so Fallon began writing more songs and put together a plan for the solo release. Following the announced hiatus of The Gaslight Anthem in July 2015, Fallon entered a Nashville studio to record Painkillers with producer Butch Walker, who also plays guitar on the album. Catherine Popper plays bass and Mark Stepro plays drums on the album.
The lead single from Painkillers, "A Wonderful Life", was premiered on The Wall Street Journal's website on December 10, 2015, a day before its digital release date of December 11, 2015. "A Wonderful Life" was then serviced to alternative radio on January 12, 2016.
Prior to the album's release, four additional songs were released to digital stores and streaming services. The songs were "Nobody Wins" (January 22), "Smoke" (February 5), "Steve McQueen" (February 19) and "Painkillers" (March 4).
Painkillers received mostly positive reviews from music critics. At Metacritic, which assigns a normalized rating out of 100 to reviews from mainstream critics, the album has an average score of 78 out of 100, which indicates "generally favorable reviews" based on 17 reviews.
Jonathan Bernstein of Rolling Stone rated the album three and a half stars out of five and writes, "Painkillers isn't quite a rebirth, but with his band struggling to stay vibrant in recent years, it feels a little like a new morning." Writing for Classic Rock, Emma Johnston states "Fallon doesn't really need the backup of a regular band. With this debut he's placed his stake as an American singer-songwriter of style and substance." In a three out of five star rating, Jess Denham of The Independent calls it "solid, genuinely inspired songwriting that The Gaslight Anthem fans will enjoy." Adam Feibel of Exclaim! rated the album eight out of ten and writes, "Fallon's songwriting is warm and varied, and there's more soul and character in his voice than ever before."