Howard spent much of his childhood growing up in the small town of Fallbrook in Northern San Diego County, before devoting himself to a full-time acting career.

[1][2][5] Howard developed an interest in martial arts at age four and began studying when his parents enrolled him at a dojo in Oceanside, California.

[5][11][12] A year later, his parents enrolled him at another dojo which specialized in the Okinawan discipline of Shōrin-ryū and at the age of seven, he began developing his extreme martial arts skills by adding gymnastics to his routine.

"[5] From a young age, Howard was a fan of Bruce Lee and Chuck Norris films, and admired their ability to incorporate martial arts into their acting.

[11][12] It was at a martial arts tournament that Howard was first spotted by someone who thought he had the looks to go into show business and referred him to their talent agent.

[1][13] In 2009, Howard landed his first steady job interviewing celebrities as "Leo Little", the host of the short-form Disney Channel talk show series, Leo Little's Big Show and made his feature film debut as "Eric Brooks" in the family film Aussie and Ted.

[2][5][13] In August of that year, Howard gained notoriety for his martial arts skills when he appeared as "Young Snake-Eyes", performing all of his own stunts in a flashback scene for the Paramount action-adventure film G.I.

[1][13][14] In November 2009, Howard began a recurring role as "Hart Hamlin" on the Disney XD series, Zeke and Luther.

[2][11][15] The film received mixed reviews, but Howard was praised for his performance, with film critic, Ty Burr of The Boston Globe writing, "The star (Jason Momoa) is arguably outshined by Leo Howard, the feral 13-year-old actor who plays the young Conan in the opening scenes.

"[16] In an interview with Empire, director Marcus Nispel spoke of working with Howard: "After we finished the film, I went to Lionsgate and said 'Y'know, the movie to do next is Conan: The Early Years.'

"[15] In June 2010, Howard landed a starring role as "Jack", a teenage karate expert who befriends a group of high school misfits on the Disney XD comedy series, Kickin' It.

In 2019, Howard landed a recurring role in Why Women Kill as "Tommy", an eighteen year-old who leads Simone, a woman dealing with a divorce after she realized her husband was gay, into having an affair with him.

[2][5] While still devoted to his passion for martial arts, Howard has stated that he has become more careful when it comes to "fighting" and "sparring" matches, due to the potential for injuries that could interfere with his obligations as an actor.