Beginning his career as a child actor, Osment's role in the comedy-drama film Forrest Gump (1994) won him a Young Artist Award.

Osment made his Broadway debut in a short-lived revival of David Mamet's play American Buffalo (2008),[2] and executive produced the independent film Montana Amazon (2012) which he also starred in.

Called back for an audition, he was asked to describe the biggest thing he had ever seen; his description of an IMAX theater screen helped win him a part in a Pizza Hut TV commercial.

[6] The commercial launched his career, and later that year he starred in the ABC TV sitcom Thunder Alley, his first role in series television.

For his portrayal of Cole Sear, a psychic child, Osment won the Saturn Award for Best Performance by a Younger Actor.

One of Osment's lines in The Sixth Sense, "I see dead people," became a popular catchphrase and is often repeated or parodied on television programs and in other media.

Osment also voiced the character of Takeshi Jin in the English version of the Immortal Grand Prix anime television series.

He appeared in Home of the Giants, playing a high school journalist opposite Ryan Merriman and Danielle Panabaker.

[16] Osment made his Broadway debut at the Belasco Theatre in November 2008 playing the role of Bobby, a young heroin addict, in a revival of David Mamet's American Buffalo; co-starring with John Leguizamo and Cedric the Entertainer.

[19] In January 2011, Entertainment Weekly reported that Osment had joined the cast of Sassy Pants, a comedy about a homeschooler with an overbearing mother.

[20] Variety reported on June 27, 2011, that Osment would star in Wake the Dead, a modern-day retelling of the Frankenstein story, with production to begin the last quarter of 2011.

Kevin Smith has further added to Osment's career resurgence with roles in the first two films of his True North Trilogy, first as Teddy Craft in Tusk and next as a fictionalized version of Canadian journalist Adrien Arcand in Yoga Hosers.

In 2017, Osment held a recurring role in season 4 of HBO's Silicon Valley as VR expert and tech financier Keenan Feldspar.

[22] He then appeared in the comedy films Izzy Gets the F*ck Across Town (2017) and Clara's Ghost (2018) In 2019, Osment had a supporting role in the Netflix film Extremely Wicked, Shockingly Evil and Vile, starring alongside Lily Collins whose character Liz follows the prosecution of Ted Bundy, played by Zac Efron.