He was born in the Glendale section of the New York City borough of Queens to a German father and Scottish-born mother. Walken has been married to casting director Georgianne Walken since 1969.

Walken initially trained as a dancer in musical theatre before moving on to more serious roles in theatre and then film. A select number of his movies include dance moves that he has worked in, reflecting this early background.

He has been in nearly one hundred movies and television shows since 1953, including The Dead Zone (1983), Brainstorm (1983), A View to a Kill (1985), Batman Returns (1992) True Romance (1993), Pulp Fiction (1994), Nick of Time (1995), Catch Me If You Can (2002) and Around the Bend (2004). He was George Lucas' second choice for Han Solo after Harrison Ford. He won the Academy Award for Best Supporting Actor in The Deer Hunter (1978) where he played a disturbed Vietnam vet alongside Robert De Niro. He was nominated again in 2002 for Catch Me if You Can.

He also has a considerable body of work in theatre, with over 100 plays to his credit. He won the Clarence Derwent award for his performance in The Lion in Winter in 1966 and an Obie for his 1975 performance in Kid Champion. He has played the main role in a number of Shakespeare plays notably Hamlet, Macbeth, Romeo and Juliet and Coriolanus. He tried his hand at writing and directing with the short five minute film Popcorn Shrimp in 2001.

In November 1981, Walken was on a yacht docked off of Catalina Island with actor Robert Wagner (as well as the skipper of the boat) when Wagner's famous wife, actress Natalie Wood, drowned.

He has also starred in three music videos. His first video role was as the Angel of Death in Madonna's 1993 "Bad Girl" video, the second appearance was in Skid Row's Breain' Down video, and the third one in Fatboy Slim's "Weapon of Choice" video in 2001.

Most recently he played the role of Morty in the comedy Click (2006)

He is, as of 2006, the only actor to play a Bond Villain and a Batman Villain.

Walken has attracted strong cult following as an actor. One reason for this is the type of films he has appeared in, for example gangster and science fiction/fantasy films, or films by directors with their own cult following such as Abel Ferrara, David Cronenberg and Quentin Tarantino. But more important factors are his odd appearance, his quirky mannerisms, his unique delivery (since high school he has kept the habit of eliminating the punctuation from his scripts) and his ability to exude menace. This cult status is demonstrated by the number of photoshopped images of Walken on the net, the frequency of impersonations either by amateurs or other professional actors (notably Kevin Spacey, Kevin Pollak, and Jay Mohr), the invention of fictitious stories about his activities and the invention of various things he might have said. There is also the fan practice of rote reciting some of his speeches from film - for example True Romance, Pulp Fiction and The Prophecy (see descriptions below). There are even short films and plays which use his persona.

Walken has hosted the New York comedy sketch and satire TV series Saturday Night Live on more than five occasions. His recurring sketch "The Continental" has been a favourite with audiences. However, his most popular SNL performance was a spoof of "Behind the Music" featuring a recording session of Blue oyster Cult's "(Don't Fear) The Reaper." In the guise of record producer Bruce Dickinson, Walken makes passionate and slightly unhinged speeches to the band. More importantly, contrary to the opinions of most of the band, he is obsessed with getting "more cowbell" into the song. This sketch has proven immensely popular and has garnered a large cult following. Walken also spoofed his role from The Dead Zone in a sketch titled "Ed Glosser: Trivial Psychic," in which the title character had the ability to accurately predict meaningless, trivial future events ("You're going to get an ice cream headache and it will last two, three minutes!"). Another notable performance was his song and dance rendition of the Irving Berlin standard "Let's Face the Music and Dance." Finally, the "Col. Angus" sketch - in which Walken played a dishonored Confederate officer named Col. Angus - was a tour de force of ribald double entendre.

As of August 2005, he was the subject of a hoax Presidential campaign. A website, Walken2008.com, presented numerous politically-charged quotes from Walken, which his publicist dismissed as "100% not true." The Urban Legends Reference Pages list the site as a fake. This hoax was perpetrated by the Internet message board General Mayhem. Ironically though, in the 2005 film, Wedding Crashers, Walken plays the Treasury Secretary of the United States who, in the motion picture, is considering a run for the presidency.