Baker received some musical education at Glendale Junior High School, but left school at the age of 16 in 1946 to join the United States Army. He was posted to Berlin, where he joined the 298th Army band. After leaving the army in 1948, he studied theory and harmony at El Camino College in Los Angeles. He dropped out in his second year, however, re-enlisting in the army in 1950. Baker became a member of the Sixth Army Band at the Presidio in San Francisco, and was soon spending time in San Francisco jazz clubs such as Bop City and the Black Hawk. In 1951, Baker once again obtained a discharge from the army to pursue a career as a professional musician.

Baker earned much attention and critical praise through the 1950s, particularly for albums featuring his vocals (Chet Baker Sings, It Could Happen to You). Jazz Historian Dave Gelly described the promise of Baker's early career as "James Dean, Sinatra, and Bix, rolled into one." His well-publicized drug habit also drove his notoriety and fame; Baker was in and out of jail frequently before enjoying a career resurgence in the late 1970s and '80s.

In 1952, Baker joined the Gerry Mulligan Quartet, which was an instant phenomenon. Several things made the Mulligan/Baker group special, the most prominent being the interplay between Mulligan's baritone sax and Baker's trumpet. Rather than playing identical melody lines in unison like bebop giants Charlie Parker and Dizzy Gillespie did, the two would complement each other's playing with contrapuntal touches, and it often seemed as if they had telepathy in anticipating what the other was going to play next. The Quartet's version of "My Funny Valentine", featuring a Baker solo, was a hit, and became a tune with which Baker was intimately associated. With the Quartet, Baker was a regular performer at Los Angeles jazz clubs such as The Haig and the Tiffany Club.

The Quartet found success quickly, but lasted less than a year because of Mulligan's arrest and imprisonment on drug charges. Baker formed his own quartet with Pianist and Composer Russ Freeman in 1953, along with bassists Bob Whitlock, Carson Smith, Joe Mondragon, and Jimmy Bond and drummers Shelly Manne, Larry Bunker, and Bob Neel. The Chet Baker Quartet found success with their live sets, and they released a number of popular albums between 1953 and 1956. In 1953 and 1954, Baker won the Down Beat and Metronome magazines' Readers Jazz Polls, beating the era's two top trumpeters, Miles Davis and Clifford Brown. Down Beat readers also voted Baker as the top jazz vocalist in 1954. In 1956, Pacific Jazz released Chet Baker Sings, a record that increased his profile but alienated some traditional jazz critics; he would continue to sing throughout his career.

Baker's chiseled features led to an approach by Hollywood studios, and he made his acting debut in the film Hell's Horizon, released in the fall of 1955. He declined an offer of a studio contract, preferring life on the road as a musician. Over the next few years, Baker fronted his own combos, including a 1955 quintet featuring Francy Boland, where Baker combined playing trumpet and singing. In 1956 Chet Baker completed an eight-month tour of Europe, where he recorded Chet Baker In Europe.

He became an icon of the West Coast "cool school" of jazz, helped by his good looks and singing talent. One of Baker's 1956 recordings, released for the first time in its entirety in 1989 as The Route, with Art Pepper, helped further the West Coast jazz sound and became a staple of cool jazz.

Baker often said he began using heroin in 1957, resulting in an addiction that lasted the remainder of his life. But in Chet Baker, his life and music by author Jeroen de Valk, Russ Freeman and others state that he was on drugs from the early '50s on. Freeman was Baker's Pianist and musical Director for a few years after Baker had left Mulligan's quartet. At times, Baker pawned his instruments for money to maintain his drug habit. In the early 1960s, he served more than a year in prison in Italy on drug charges; he was later expelled from both West Germany and the United Kingdom for drug-related offenses. Baker was eventually deported from West Germany to the United States after running afoul of the law there a second time. He settled in Milpitas in northern California, where he played in San Jose and San Francisco between short jail terms served for prescription fraud.

Baker was reportedly the inspiration for the character Chad Bixby, played by Robert Wagner in the 1960 film All the Fine Young Cannibals. Another film, to be titled Prince of Cool, about Baker's life, was cancelled as of January 2008.

In 1966, Baker was savagely beaten (allegedly while attempting to buy drugs) after a gig in The Trident restaurant in Sausalito, California, sustaining severe cuts on the lips and supposedly broken front teeth, which ruined his embouchure. He stated in the film Let's Get Lost that an acquaintance attempted to rob him one night but backed off, only to return the next night with a group of several men who chased him. He entered a car and became surrounded. Instead of rescuing him, the people inside the car pushed him back out onto the street, where the chase by his attackers continued, and subsequently he was beaten to the point that his teeth, never in good condition to begin with, were knocked out, leaving him without the ability to play his trumpet. He took odd jobs, among them pumping gas. In a 1980 interview he stated that he worked for a long time at a gas station, working 7 am to 11 pm until he came to the conclusion that he needed to find a way to return to his music. Meanwhile, he was fitted for dentures and worked on his embouchure. Three months later he got a gig in New York City. In Chet Baker, his life and music, biographer Jeroen de Valk writes that Baker only lost one part of one tooth at the aforementioned fight, kept on performing for a while - 'and initially not badly at all', until he was fitted with dentures a few years later.

After developing a new embouchure resulting from dentures, Baker returned to the straight-ahead jazz that began his career. He relocated to New York City and began performing and recording again, including with Guitarist Jim Hall. Later in the 1970s, Baker returned to Europe, where he was assisted by his friend Diane Vavra, who took care of his personal needs and otherwise helped him during his recording and performance dates.

From 1978 until his death in 1988, Baker resided and played almost exclusively in Europe, returning to the U.S. roughly once a year for a few performances. This was Baker's most prolific era as a recording Artist. However, as his extensive output is strewn across numerous, mostly small European labels, none of these recordings ever reached a wider audience, even though many of them were well received by critics, who maintain that the period was one of Baker's most mature and rewarding. Of particular importance are Baker's quartet featuring the Pianist Phil Markowitz (1978–80) and his trio with Guitarist Philip Catherine and Bassist Jean-Louis Rassinfosse (1983–85). He also toured with Saxophonist Stan Getz during this period.

In 1983, British singer Elvis Costello, a longtime fan of Baker, hired the trumpeter to play a solo on his song "Shipbuilding" for the album Punch the Clock. The song exposed Baker's music to a new audience. Later, Baker often featured Costello's song "Almost Blue" (inspired by Baker's version of "The Thrill Is Gone") in his concert sets, and recorded the song for Let's Get Lost, a documentary film about his life.

In 1986, Chet Baker: Live at Ronnie Scott's London presents Baker in an intimate stage performance filmed with Elvis Costello and Van Morrison as he performs a set of standards and classics, including "Just Friends", "My Ideal", and "Shifting Down". Augmenting the music, Baker speaks one-on-one with friend and colleague Costello about his childhood, career, and struggle with drugs. Although Baker was not in great shape during the concert, the interview is highly informative.

The video material recorded by Japanese television during Baker's 1987 tour in Japan showed a man whose face looked much older than he was, but his trumpet playing was alert, lively and inspired. Baker recorded the live album Chet Baker in Tokyo with his quartet featuring Pianist Harold Danko, Bassist Hein Van de Geyn and Drummer John Engels less than a year before his death, and it was released posthumously. Silent Nights, a recording of Christmas music, was recorded with Christopher Mason in New Orleans in 1986 and released in 1987.

Baker was photographed by william Claxton for his book Young Chet: The Young Chet Baker. An Academy Award-nominated 1988 documentary about Baker, Let's Get Lost, portrays him as a cultural icon of the 1950s, but juxtaposes this with his later image as a drug addict. The film, directed by fashion Photographer Bruce Weber, was shot in black-and-white and includes a series of interviews with friends, family (including his three children by third wife Carol Baker), associates and women friends, interspersed with film from Baker's earlier life, and with interviews with Baker from his last years. In Chet Baker, his life and music, author De Valk and others criticize the film for presenting Baker as a washed-up musician in his later years. The film was shot during a few weeks in the first half of 1987 and ignores later highlights such as the aforement Japanese concert.

The documentary Chet Baker, the last days (1989) by Dutch Director Willem Ouwerkerk concentrates on his career as a musician.

In 1991, singer-songwriter David Wilcox recorded the song "Chet Baker's Unsung Swan Song" on his album Home Again, speculating on what might have been Baker's last thoughts before falling to his death. The song was later covered by k.d. lang as "My Old Addiction" on her 1997 album Drag. The song "Chet Baker", which appears on the 2007 CD Wally Page and Johnny Mulhern: Live at the Annesley House, by Irish folk singer-songwriter Wally Page, describes the end of Baker's life in Amsterdam.

Time after Time: The Chet Baker Project, written by Playwright James O'Reilly, toured Canada in 2001 to much acclaim. The musical play Chet Baker – Speedball explores aspects of his life and music, and was premiered in London at the Oval House Theatre in February 2007, with further development of the script and performances leading to its revival at the 606 Club in the London Jazz Festival of November 2007.

Brazilian jazz Pianist Eliane Elias dedicated her 2013 album I Thought About You to Chet Baker. Brazilian vocalist Luciana Souza also pays tribute to Baker on her 2012 album The Book of Chet.

Jeroen de Valk has written a biography of Baker which is available in several languages: Chet Baker: His Life and Music is the English translation. Other biographies include James Gavin's Deep in a Dream—The Long Night of Chet Baker, and Matthew Ruddick's Funny Valentine. Baker's "lost memoirs" are available in the book As Though I Had Wings, which includes an introduction by Carol Baker.

He is portrayed by Ethan Hawke in the 2015 film Born to Be Blue. It is a reimagining of Baker's career in the late 1960s, when he is famous for both his music and his addiction, and he takes part in a movie about his life to boost his career.

Early 2016, trumpeter Edu Ninck Blok issued the CD Traces of Chesney / A tribute to Chet Baker (Silence! Records). Ninck Blok worked with Baker both on stage and in the recording studio, most notably when Baker guested with Ninck Blok’s Amstel Octet (The Amstel Octet & Chet Baker, Challenge Records). Both albums feature Drummer and Baker veteran John Engels as well.