Avriel Benjamin Kaplan was born in Visalia, California, where he was also raised. He has a brother, Joshua Kaplan, and a sister, Esther Koop, who is Pentatonix’s tour manager as of April 2018.  He is Jewish, which was the cause of vast bullying as a child. 
He loved folk music, and frequently went to the nearby Sequoia National Park, which became an inspiration for his music. He considers his musical inspirations to be Simon & Garfunkel, John Denver, Crosby, Stills, Nash & Young, and Bill Withers. Later inspirations include Iron & Wine, Bon Iver, Ben Harper, and José González
Before joining Pentatonix, Kaplan was already an accomplished a cappella artist, performing in the styles of jazz and opera among others. 
He joined Pentatonix in 2011, when original members Kirstin Maldonado, Mitch Grassi and Scott Hoying were searching for a bass singer and a beatboxer. The group met the day before the auditions for the third season of The Sing-Off began.  The group successfully auditioned for the show and eventually went on to win the title for 2011 (season three).  Kaplan acted as the group’s vocal bass, but frequently sang lead parts as well.
As a member of Pentatonix, Kaplan won three Grammy awards. On February 8, 2015, Pentatonix won a Grammy in the “Best Arrangement, Instrumental or A cappella” category for their song “Daft Punk,” a medley of songs by Daft Punk.  On February 15, 2016, Pentatonix won a Grammy in the same category, this time for their rendition of “Dance of the Sugar Plum Fairy” from their That’s Christmas to Me album.  On February 12, 2017, Pentatonix won a Grammy in the “Best Country duo / group performance” category for their cover of “Jolene,” which featured Dolly Parton. 
On April 29, 2017, Kaplan premiered “Fields and Pier,” his first song as a solo artist, under the name “Avriel & the Sequoias.”  In May 2017, Kaplan announced that he would be leaving Pentatonix to spend more time with friends and family.  His debut EP, Sage and Stone, was released on June 9, 2017. 
In October 2019, he announced a European tour, his first since leaving Pentatonix. 
On November 5, 2019, he announced an upcoming EP, “I’ll Get By”, set to be released January 24, 2020, along with an accompanying tour.   On January 21, 2020, the release was postponed to February 28 as a result of being signed to Fantasy Records. 
Kaplan is a co-founder of A Cappella Academy, a camp established in 2014 for 12-18 year-old kids to learn about a cappella.