Valensi has also worked as a songwriter and session guitarist with various artists, including Sia, Regina Spektor, Kate Pierson, Kesha and Ringo Starr.

[7] His father described him as a natural guitarist, due to his quickness at picking up the ability to strum along with the rhythm of songs at a young age.

[12][13] Nikolai Fraiture started playing as the bassist and the band was formed when guitarist Albert Hammond Jr. joined in fall 1998.

He is the frontman of the group, and is backed by drummer Ralph Alexander, multi-instrumentalist Brad Oberhofer, bassist Jon Safley, and guitarist Darian Zahedi.

Valensi has described the band's sound as a mix of power pop and heavy metal, and has named The Cars, Cheap Trick and Elvis Costello as influences.

[21] While much of his career has been focused on playing and writing for The Strokes and CRX, Valensi has also contributed as a session musician and songwriter to some of his contemporaries.

Nick Valensi sang backing vocals and played guitar for Devendra Banhart's song "Shabop Shalom" on the 2007 album Smokey Rolls Down Thunder Canyon.

Other credits include co-writing with Brody Dalle in 2014, Kate Pierson for her 2015 album Guitars and Microphones,[24][25] Kesha, and again with Sia for the 2017 Blondie track, "Best Day Ever."

Valensi's main guitar, which he uses for nearly every live show and recorded song, is a 1995 Epiphone Riviera with Gibson P-94 pick-ups, which was given to him by friend and fellow Strokes guitarist Albert Hammond Jr.

[citation needed] He cites his influences as The Velvet Underground, The Cars, George Harrison, Slash, Bob Marley, and Blondie.

[26] In summer 2006, Valensi married his girlfriend of five years, English photographer and television personality Amanda de Cadenet.

De Cadenet published a book of photographs entitled Rare Birds in 2005, which includes several pictures of Valensi, whom she refers to as her "muse" on her website.