At the age of 11 he secured his first professional role, playing Clarence in the West End show Whistle Down the Wind (Aldwych Theatre, 1998).

He is best known for his portrayal of Jay Cartwright in the award-winning E4 sitcom, The Inbetweeners (2008-2010), which co-starred Simon Bird, Blake Harrison and Joe Thomas.

[4] He then played the young Del Boy in the BBC comedy-drama Rock & Chips (2010-2011), a prequel to the sitcom Only Fools and Horses, created and written by John Sullivan.

He worked again with the creators and writers of The Inbetweeners, and was reunited with his former co-star, Joe Thomas, for two series of the sitcom White Gold, set in 1980s Essex, and broadcast on BBC Two between 2017 and 2019.

For Red Nose Day 2011, Buckley and his Inbetweeners co-stars went on a "rude road trip" and visited the rudest street names in the United Kingdom in 50 hours.

[13] In October 2024, it was revealed that he would star alongside Martin Clunes in the British comedy drama, Mother's Pride, expected in cinemas in 2025.

[14] Buckley’s stage career began at the age of 11 when he played Clarence in the West End musical, Whistle Down the Wind (Aldwych Theatre, 1998).

[17] In 2005 Buckley appeared in the music video for the Gravenhurst’s track "I Turn My Face To The Forest Floor" directed by Ralitza Petrova.

[18] He starred in the music video for States of Emotion's track "The Unsung",[19] and also featured on Steve Cradock's album, Peace City West (2011), playing guitar and providing backing vocals.

[20] In 2012, Buckley made his directorial debut with a music video for the track, "Every Time We Fight" (2012) for the Essex band, The Milk.

[23] He has provided voice-overs for Envirofone, Trunki and Hastings Direct, and has also appeared in commercials for Orange (with the cast of The Expendables 2), Game, and bookmaker Ladbrokes.

In 2020, Oldham Council commissioned him to produce a Cameo video message outlining safety measures they had put in place to help stop the spread of coronavirus.

In April 2016, Buckley began a YouTube gaming channel called Completed It Mate — a reference to The Inbetweeners episode "Will's Dilemma"[25] — which has over 428,000 subscribers as of September 2021.

Since beginning his channel, Buckley has collaborated with other YouTubers, most notably with the Rooster Teeth group Achievement Hunter, when he appeared on their Off Topic Podcast and multiple episodes of their Let's Play series.