Dier was born on February 14, 1990 in London, Ontario. He studied improv as well as receiving his first dan black belt in Taekwondo. He reached the 6th grade of Conservatory Music in piano, including the Suzuki method since the age of 4. He also plays the guitar.
In 2006, Dier received his debut role as Matt Peterson in the TV movie, Family in Hiding. In 2007, he appeared in Seventeen and Missing and The Secrets of Comforting House.
In April 2018, actress Haley Lu Richardson revealed that she and Dier were engaged, having proposed to him. They have been in a relationship since 2012.