Farro was born in Voorhees Township, New Jersey on September 29, 1987. He is the second-oldest of his other four siblings, including former Paramore drummer Zac Farro. Farro is three quarters Italian. He is a self-taught guitarist, and began playing when he was 13 years old.
Along with his younger brother Zac, Farro was a founding member of Paramore serving as the band's lead guitarist and backing vocalist from 2004 until his exit in late 2010. Farro also co-wrote almost every track on Paramore's first three albums with Hayley Williams and occasionally Taylor York.
On December 21, 2010, a blog appeared online claiming to be an official exit statement from the Farro brothers. The blog entry refuted statements made by Paramore's official website regarding the brothers' departure and was heavily critical of Hayley Williams, her family, Atlantic Records and Fueled by Ramen.
Farro appeared in a video on YouTube claiming that the blog was genuine. The video was quickly removed for reported violations but Farro re-uploaded the video a few days later.
He was one of three co-writers to the song "This is Amazing Grace". It was Josh Farro, Jeremy Riddle and Phil Wickham who wrote the song and it is featured on both, Bethel Music's (Bethel Church) live CD/DVD "For The Sake Of The World" where Jeremy performed it, as well as on Phil Wickham's album "The Ascension".