Harrison James Osterfield was born on July 4, 1996 in Surrey, England, United Kingdom to his parents. He was raised near West Sussex with his younger half-sister, Charlotte. For six years, Harrison attended Caterham School, a co-educational day and boarding school, as a boarding school student. While attending, he was in the drama club and participated in school plays, which encouraged him to enroll in the BRIT School, a performing arts and technology school. While attending BRIT School, Harrison starred in countless short films and became close friends with Tom Holland. After, he was accepted into the foundation course at the London Academy of Music and Dramatic Art. Once Harrison graduated, he served as Tom Holland’s personal assistant, beginning with Spider-Man: Hoomecoming, where he would also be seen as an extra in.

Harrison’s short film credits include playing Orphan in 2014’s Trepidation, Edward Lucas in Supply and Demand as well as the football player in Colours in 2015; followed by Ethan Adler’s Guide to Homicide as Ethan Adler and Spooner in One in a Million in 2017 and as Parker in 2018’s Vent. He had an uncredited role in Peter Parker’s school bus scene at the beginning of Avengers: Infinity War. Harrison would next play Snowden in an episode of the television mini-series Catch-22 in 2019. The series is an adaption of the classic Joseph Heller novel, starring Kyle Chandler, Christopher Abbott, and George Clooney. The same year, he created a comedy podcast called Village People with his friend Greg Birks.

In 2021, Harrison landed the role of Leopold, a prince who stumbles across the other characters and decides to tag along, on the Netflix fantasy drama The Irregulars alongside McKell Devid, Thaddea Graham, and Jojo Macari. The series follows a gang of troubled street teens who are manipulated into solving crimes for the sinister Doctor Watson and his mysterious business partner, one Sherlock Holmes. He would also have an uncredited role of the Farnbranch Man in Chaos Walking, an action fantasy film starring Tom Holland and Daisy Ridley. Harrison was originally only supposed to be an extra, but after the director saw him in costume, he initially had another character share his lines with Harrison, but in the end, Harrison won the part of the actor casted.

Harrison filmed Cranley Gardens, a film starring Jennifer Tao and Gianni Capaldi, and will portray the role of Jake. The film is currently in the post-production process.