Hopper moved to New York and studied at the famous Lee Strasberg acting school. He appeared in over 140 episodes of television shows such as Bonanza, The Twilight Zone, The Defenders, The Big Valley, The Time Tunnel and Combat. Hopper also became an accomplished professional photographer (he has had many exhibitions of his work). He also was very talented as a painter and a poet.

Hopper had a supporting role as "Babalugats," the bet-taker in Cool Hand Luke (1967).

Although Hopper was able to resume acting in mainstream films including The Sons of Katie Elder (1965) and True Grit (1969), in both of these films he had death scenes with John Wayne. It was not until he teamed with Peter Fonda and Jack Nicholson and made Easy Rider that he really shook up the Hollywood establishment. This film became an anthem of sorts to the lost generation of the Vietnam war and to this day is one of the most successful independent films ever made. Hopper won wide acclaim as the director of the film for his improvisational methods and stop action photography.

Hopper wrote and directed another film that was released in 1971 called The Last Movie that was a box office failure and derailed his career for years. Hopper had long been an alcoholic and drug abuser and it was at this point his addiction began to dominate his life. However, Hopper did act in several films during this period such as Mad Dog Morgan (1976), Tracks (1976), The American Friend (1977) and Apocalypse Now (1979), and he won acclaim for directing and acting in Out of the Blue (1980).

Immediately thereafter, Hopper also starred as an aging freebase-addled rock star in the low-budget Neil Young-Dean Stockwell collaboration Human Highway with the new wave group Devo. Production was often delayed by his unreliable behavior. Interestingly, Hopper's character clearly parallels the then-concurrent problems of David Crosby, who served as the basis for Billy in Easy Rider. Peter Biskind states in the New Hollywood history Easy Riders, Raging Bulls that Hopper's cocaine intake had reached three grams a day by this time period, complemented by an additional thirty beers and numerous cuba libres.

In 1983 Hopper entered a drug rehabilitation program, spent time in a state institution, and cured himself of his addictions. He gave powerful performances in Rumble Fish (1983) and The Osterman Weekend (1983). However, it was not until he portrayed the alkyl nitrites-huffing, obscenity-screaming Frank Booth in David Lynch's film Blue Velvet (1986) that his career truly revived. After reading the script, Hopper called Lynch and told him "You have to let me play Frank Booth. Because I am Frank Booth!" Hopper won critical acclaim and a slew of awards for this role and the same year won an Oscar nomination for Best Supporting Actor for Hoosiers.

In 1988, Hopper directed a critically acclaimed film about Los Angeles gangs called Colors. He has continued to be an important actor, photographer and director. He was nominated for an Emmy award for the 1991 HBO films Paris Trout and Doublecrossed (in which he played real life drug smuggler and DEA informant Barry Seal). He also co-starred in the 1994 blockbuster Speed with Keanu Reeves and Sandra Bullock. He recently contributed to the film 1 Giant Leap with provocative anecdotes on spirituality, unity and culture.

Hopper teamed with Nike in the early 1990s to make a series of successful television commercials. He appeared as a "crazed referee" in those ads.

He starred as villain Victor Drazen in the first season of the popular Fox drama 24. In an attempt to put on a Serbian accent to better portray his role, he ended up sounding like a German/Russian guy. Hopper is most recently starring in the NBC 2006 television series E-Ring, a drama set at The Pentagon.

On the 2005 Gorillaz album Demon Days, Hopper performs the spoken word track "Fire Coming Out of the Monkey's Head."

Despite being famous as an actor and director, Hopper sees himself primarily as an artist, and is an accomplished and much-respected painter, art collector and photographer: