Schultz has stated, "I write the lyrics, and I co-write the songs with Jer," adding "It's never the same thing with each song. Generally speaking it involves a piano, a guitar, and maybe singing, and we usually start out with the chord structure, a set of chords, a melody especially, and then the lyrics usually follow. Or it's one phrase that you really find great and then you build the song around that." Schultz later claimed, "Your melodies make people want to hear what you're saying," adding, "They've got to be open to hearing it, almost hum it. And if they want to go deeper there is something there."

Fraites emphasizes the simplicity of the group's style, stating, "we're not reinventing the wheel or doing anything that different, the songs are super simple. The ideas themselves are very simple ideas. Anyone who can play an instrument can play a Lumineers song. I think there's a certain cinematic aspect of our music that I really like." Launchpad similarly writes, "where most bands these days look for that new, original sound to enhance the digital revolution, 'The Lumineers' do superbly in taking it back to simplicity." In another interview, Fraites explains, "I just think people are enamored of going into a room and watching people play their own instruments and sing, rather than using Auto-Tune and a lot of digital equipment to get their sound across. There is so much digital-ness all around us. People are almost taken aback when you do the opposite of that. It's inspiring."

Alister Roberts of Contactmusic has described the band's self-titled debut album as, "a perfectly formed collection of rustic folk type songs, slotting in nicely amongst the current roots revival." Their folk sound has received comparisons to Mumford & Sons. On Mumford & Sons, Schultz has commented that they, "kicked down doors, and they allowed radio to receive a band like us because we somehow slightly resemble what they're doing." Jon Pareles of The New York Times wrote that, "Mumford comparisons rankle the Lumineers. While both bands wrap moody lyrics in toe-tapping melodies, Mumford & Sons pile on instruments in massive buildups. The Lumineers, by contrast, stay sparse, barely getting around to using an electric guitar on The Lumineers."

Other artists have commented on the folk-style music of The Lumineers and Mumford & Sons; alternative rock artist Jack White praised the style, stating, "I think these acts nowadays are keeping people's ears open to the idea of the soulfulness of folk-style music and acoustic music, and you get a little bit closer to the musician, to the writer, at times." Conversely, hard and shock rock artist Alice Cooper criticized the two bands, calling it "an offense" to label them rock bands.

The band cites a diverse range of influences, including Bob Dylan, Beethoven, Guns N' Roses, Talking Heads, Bruce Springsteen, Pearl Jam, The Cars, Leonard Cohen, and "cinematic music and anything strange and weird." Schultz adds Bob Dylan, Born in the U.S.A., Greatest Hits, Sand in the Vaseline, Exile on Main St., and The Future as specific album influences. Additionally, Schultz cites a Tom Petty performance as one that "really stands out" to him, stating "I just remember him playing "Last Dance With Mary Jane", and as the opening guitar line was being played, he opened up a chest on stage that had not been opened the entire show, pulled out a hat, put that hat on for the duration of the song, and then opened the chest back up and put it in and shut it. That is the moment I took away from his show. This taught me everything I needed to know."

• The Lumineers (2012)
• Cleopatra (2016)
• III (2019)
• Brightside (2022)
• Automatic (2025)