Hamilton Nash Grier was born and raised in North Carolina by mother Elizabeth Floyd and father Chad Grier, who is now one of his managers. He is the second-oldest child with an older brother, Will Grier, a football quarterback who was drafted by the Carolina Panthers in the 2019 NFL Draft; a younger brother, Hayes, who also posted vines; and a younger half-sister, Skylynn, whom his mother had with her current husband, John Floyd.
Nash Grier was a freshman at Davidson Day School when the mobile app Vine was released, a social media platform which allows users to post looping 6-second videos for others to view. Grier began to post comedy-related videos for friends and classmates and quickly amassed a wider fanbase.
Shortly after Grier's rise to Internet fame, he joined the touring group Magcon (Meet and Greet Convention), a convention where fans could meet and interact with Internet personalities. There were multiple shows in the major cities of the U.S. between 2013 and 2014. Other Vine celebrities on the tour included Cameron Dallas, whom he met over the app, Matthew Espinosa, Jack Gilinsky, Jack Johnson, Aaron Carpenter, Taylor Caniff, Shawn Mendes, Jacob Whitesides, Carter Reynolds, Mahogany Lox, and his brother Hayes Grier. In early 2014, Grier along with a few other members quit Magcon as they felt that it limited their future careers and were interested in pursuing other goals. In summer of 2014 at 16 years of age, Grier moved to Los Angeles where he bought his first apartment with Dallas so they could be closer to their management (26MGMT) and to also pursue careers in acting. The two along with their photographer Bryant Eslava lived there for nine months until they were evicted. Grier currently lives in a new house located in Beverly Hills. After moving to California, Grier started online schooling to complete his high school education which he has recently graduated from.
In April 2013, Grier posted a Vine in which he said, "Yes, it is! Fag!" in response to an OraQuick at-home oral HIV test ad which stated, "Testing for HIV... It's not a gay thing." Grier later deleted the vine but a recording of it resurfaced in July 2014 and Grier faced renewed scrutiny. Grier posted an apology on Twitter noting that he was "young, ignorant, stupid and in a bad place. I've moved on and learned from my mistakes and I am so truly sorry to anyone I have offended."
Grier and other members of his management have released mobile games and social media apps including Cash Dash, Mobli, and Challenged. Grier has his own website where fans can buy his merchandise as well as an Aéropostale clothing line called "UnitedXXVI," designed in part by Grier, Dallas, and younger brother Hayes. Aéropostale faced backlash for partnering with Grier due to his earlier controversies. BuzzFeed News noted "the backlash highlights the challenges brands face in working with today’s new breed of celebrity in a supremely competitive landscape."
Grier has stated that he is mostly self-taught on how to edit videos, and his 'apparent spontaneity' is actually shrewdly crafted and scripted, with clips refilmed many times and sometimes edited for hours. As of May 2016, Nash has over 12.7 million Vine followers, 4.78 million subscribers on his YouTube channel, 4.8 million Twitter followers and over 9.1 million followers on his Instagram account. His second Vine account, "Nash Grier 2", where he posts less scripted videos, has more than 2.4 million followers. Grier's management has confirmed that major brands will pay Grier anywhere between $25,000–$100,000 to advertise their products in his Vines. Because of his popularity, Grier has appeared on various news shows including Good Morning America and The View.
Grier's first major acting role was in Fullscreen's The Outfield, which premiered November 10, 2015, worldwide on the iTunes Store. He also directed a music video for singer Bera called "I Look Good On You" which was released on Grier's YouTube Channel. In 2017, Grier appeared in You Get Me with co-star Bella Thorne.
Grier is engaged to Taylor Giavasis, whom he has dated since 2015. In April 2019, the couple announced that they are expecting a child.