Hickman’s first screen appearances were as an extra in The Grapes of Wrath (1939) and Men of Boys Town (1941), in which his brother Darryl was featured. Other early screen appearances were in the 1942 Our Gang comedy Melodies Old and New, Captain Eddie (1945), The Hoodlum Saint (1946), and Faithful in My Fashion (1946).

In 1946, Hickman played young Chase in the movie The Secret Heart which starred Claudette Colbert, Walter Pidgeon, Lionel Barrymore, and June Allyson.

Hickman played different small roles in some of Columbia Pictures’ eight-film “Rusty” series, about a boy and his valiant German Shepherd: The Return of Rusty (1946), For the Love of Rusty (1947), The Son of Rusty (1947), My Dog Rusty (1948), Rusty Leads the Way (1948), Rusty’s Birthday (1949), and Rusty Saves a Life (1949). Heaven Only Knows (1947), in which he appeared, starred Bob Cummings, who would play a major role in Hickman’s career. Hickman also appeared in Her Husband’s Affairs (1948), The Boy with Green Hair (1948), The Sun Comes Up (1949), Mighty Joe Young (1949), and The Happy Years (1950), which starred Darryl. As a teen, Dwayne and Darryl guest-starred in a 1950 episode of The Lone Ranger titled “Two Gold Lockets.”

Born in Los Angeles, California, Hickman is the younger brother of child actor Darryl Hickman (b. 1931) and the older brother of Deidre Hickman (b. 1940). He graduated from Cathedral High School in 1952 and intended to become a Passionist priest, but ultimately chose not to and attended Loyola Marymount University.

Hickman focused on his studies for a few more years, then returned to acting with appearances in Public Defender, The Loretta Young Show, Lux Video Theatre, and Waterfront. In 1955, Dwayne appeared in another Lone Ranger episode titled “Sunstroke Mesa”.

In 1958, Hickman was cast as the lead of The Many Loves of Dobie Gillis, which aired on CBS from 1959–63. Although at the show’s debut the Dobie character was a teenager in high school, Hickman was then 25 years old.

During the series’ run Hickman did the voice for Aladdin in 1001 Arabian Nights (1959). On June 23, 1960, Hickman appeared on NBC’s The Ford Show, Starring Tennessee Ernie Ford.

In 1965, Hickman appeared in the comedy film Cat Ballou with Jane Fonda and Lee Marvin.