Wallach was born in Red Hook, Brooklyn, at 156 Union St., a son of Jewish immigrants Abraham and Bertha (Schorr) Wallach, both from Poland. He had a brother and two sisters, with his family being the only Jews in an otherwise Italian American neighborhood. His parents owned Bertha’s Candy Store. Wallach graduated in 1936 from the University of Texas at Austin with a degree in history. While at the university, he performed in a play with fellow students Ann Sheridan and Walter Cronkite. In a later interview, Wallach said that he learned to ride horses while in Texas, adding that he liked Texas because “it opened [his] eyes to the word friendship.” He explained, “You could rely on people. If they gave you their word, that was it … It was an education.”

Two years later he received a master of arts degree in education from the City College of New York. He gained his first method acting experience at the Neighborhood Playhouse School of the Theatre in New York City, where he studied under Sanford Meisner. There, according to Wallach, actors were forced to “unlearn” all their physical and vocal mannerisms, while traditional stage etiquette and “singsong” deliveries were “utterly excised” from his classroom.  Wallach’s education was cut short when he was drafted into the Army in January 1941. He served as staff sergeant in a military hospital in Hawaii and later sent to Officer Candidate School (OCS) in Abilene, Texas to train as a medical administrative officer. Commissioned a second lieutenant, he was ordered to Casablanca. Later, when he was serving in France, a senior officer noticed his acting career and asked him to create a show for the patients. He and his unit wrote a play called Is This the Army?, which was inspired by Irving Berlin’s This Is the Army. In the comedic play, Wallach and the other actors mocked Axis dictators, with Wallach portraying Adolf Hitler.

Wallach took classes in acting at the Dramatic Workshop of the New School in New York with the influential German director Erwin Piscator. He later became a founding member of the Actors Studio, taught by Lee Strasberg. There, he studied more method acting technique with founding member Robert Lewis, and with other students including Marlon Brando, Montgomery Clift, Herbert Berghof, Sidney Lumet, and his soon-to-be wife, Anne Jackson. Wallach became Marilyn Monroe’s first new friend when she became a student at the Actors Studio, once insisting on watching him perform in The Teahouse of the August Moon from the backstage wings, simply to see up close how experienced actors perform a two-hour play. She also became friends with his wife, Anne Jackson, also studying at the Studio, and would visit the couple at their home and sometimes babysit their new child.

In 1945 Wallach made his Broadway debut and he won a Tony Award in 1951 for his performance alongside Maureen Stapleton in the Tennessee Williams play The Rose Tattoo. His other theater credits include Mister Roberts, The Teahouse of the August Moon, Camino Real, Major Barbara (in which director Charles Laughton discouraged Wallach’s established method acting style), Luv, and Staircase, co-starring Milo O’Shea, which was a serious depiction of an aging homosexual couple. He also played a role in a tour of Antony and Cleopatra, produced by the actress Katharine Cornell in 1946. He exposed Americans to the work of playwright Eugène Ionesco in plays like The Chairs and The Lesson in 1958, and in 1961 Rhinoceros opposite Zero Mostel. He last starred on stage as the title character in Visiting Mr. Green.

The stage was where Wallach focused his early career. From 1945 to 1950 he and his wife, Anne Jackson, worked together acting in various plays by Tennessee Williams. The five years following, he continued only working on stage, not becoming involved in film work until 1956. During those years, however, they were generally having a hard time making ends meet. He recalls they were getting along on unemployment insurance and living in a one-room, $35 a month apartment on lower Fifth Avenue in the Village. When he did get offered early movie parts, he turned them down with no regrets, and very early in his career he explained his reasoning:

What do I need a movie for? The stage is on a higher level in every way, and a more satisfying medium. Movies, by comparison, are like calendar art next to great paintings. You can’t really do very much in movies or in television, but the stage is such an anarchistic medium.  He said that the stage was what attracted him most and what he “needed” to do. “Acting is the most alive thing I can do, and the most joyous,” he stated.

Wallach and Jackson became one of the best-known acting couples in the American theater, as iconic as Alfred Lunt and Lynn Fontanne, and Jessica Tandy and Hume Cronyn, and they looked for opportunities to work together. During an interview, he said of Jackson, “I have tremendous respect and admiration for her as an actress. . . we have a terrific working compatibility when we’re in the same play, especially when the play means something important to us.” When he did gravitate toward accepting parts in films, he did so to “help pay the bills,” he said, adding, “for actors, movies are a means to an end.”

Despite the fact that he eventually acted in over 90 films and almost as many television dramas, he continued to accept stage parts throughout his career, often with Jackson. They played in comedies like The Typists and The Tiger in 1963, and acted together in Waltz of the Toreadors in 1973. In 1978 they played in a revival of The Diary of Anne Frank, along with their daughters, and in 1984 they acted in Nest of the Wood Grouse, directed by Joseph Papp. Four years later, in 1988, they acted in a revival of Cafe Crown, a portrait of the Yiddish theatre scene during its prime. They continued acting together as late as 2000, while he also took on roles alone throughout all those years.

Wallach’s film debut was in Elia Kazan’s controversial 1956 Baby Doll, for which he won the British Academy Film Awards (BAFTA) as “Most Promising Newcomer.” Baby Doll was controversial because of its underlying sexual theme. Director Elia Kazan however, set explicit limits on Wallach’s scenes, telling him not to actually seduce Carroll Baker, but instead to create an unfulfilled erotic tension. Kazan later explained his reasoning:

What is erotic about sex to me is the seduction, not the act … The scene on the swings with Eli Wallach and Carroll Baker in Baby Doll is my exact idea of what eroticism in films should be.  Wallach went on to a prolific career as “one of the greatest ‘character actors’ ever to appear on stage and screen,” notes Turner Classic Movies, acting in over 90 films. Having grown up on the “mean streets” of an Italian American neighborhood, and his versatility as a method actor, Wallach developed the ability to play a wide variety of different roles, although he tried to not get pinned down to any single type of character. “Right now I’m playing an old man,” he said at age 84. But “I’ve been through all the ethnic groups, from Mexican bandits to Italian Mafia heads to Okinawans to half-breeds, and now I’m playing old Jews. Who knows?”

Noting this versatility as a character actor, the Academy of Motion Picture Arts and Sciences called him “the quintessential chameleon,” with the ability to play different characters “effortlessly,” and L.A. Times theater critic Charles McNulty saw Wallach’s “power to illuminate” his various screen or stage personas as being “radioactive.” The Guardian newspaper has written that “Wallach was made for character acting,” and includes movie clips from some of his most memorable roles in a tribute to him.  In 1961, Wallach co-starred with Marilyn Monroe, Montgomery Clift and Clark Gable in The Misfits, Monroe’s last film before her death. Wallach never learned why he was cast in the film, although he suspected that Monroe had something to do with it. Its screenwriter, Arthur Miller, who was married to Monroe at the time, said that “Eli Wallach is the happiest good actor I’ve ever known. He really enjoys the work.”

Some of his other films included The Lineup (1958), Lord Jim (1965) with Peter O’Toole, a comic role in How to Steal a Million (1966) with Audrey Hepburn, and as Tuco (the ‘Ugly’) in Sergio Leone’s The Good, the Bad and the Ugly (1966) with Clint Eastwood, followed by other Spaghetti Westerns, such as Ace High. At one point, Henry Fonda had asked Wallach whether he himself should accept a part offered to him to act in a similar Western, Once Upon a Time in the West (1968), which would also be directed by Leone. Wallach said “Yes, you’ll enjoy the challenge,” and Fonda later thanked Wallach for that advice.  Wallach and Eastwood became friends during the filming of The Good, the Bad and the Ugly and he recalled their off-work time together: “Clint was the tall, silent type. He’s the kind where you open up and do all the talking. He smiles and nods and stores it all away in that wonderful calculator of a brain.” In 2003 Wallach acted in Mystic River, produced and directed by Eastwood, who once said “working with Eli Wallach has been one of the great pleasures of my life.”

A pivotal moment in Wallach’s career came in 1953, when he along with Frank Sinatra and Harvey Lembeck tried out for the role of Maggio in the film From Here to Eternity. Sinatra biographer Kitty Kelly notes that while Sinatra’s test was good, it had none of the “consummate acting ability” of Wallach. Producer Harry Cohn and director Fred Zinnemann were “dazzled” by Wallach’s screen test and wanted him to play the part. However, Wallach had previously been offered an important role in another Tennessee Williams play, Camino Real, to be directed by Elia Kazan, and turned down the movie role. Wallach said that when he learned that the play had finally received financing, he “grabbed” the opportunity: “It was a remarkable piece of writing by the leading playwright in America and it was going to be directed by the country’s best. There really wasn’t much of a choice for me.” The film, however, went on to win eight Academy Awards, including one for Sinatra, which revived his career. Wallach recalled afterwards, “Whenever Sinatra saw me, he’d say, ‘Hello, you crazy actor!'”

Film historian James Welsh states that during Wallach’s career, he appeared in most of the “prestige” television dramas during the “Golden Age” of the 1950s, including Studio One, The Philco Television Playhouse, The Armstrong Circle Theatre, Playhouse 90, and The Hallmark Hall of Fame, among others. He won the 1966–1967 Emmy Award for his role in the telefilm The Poppy is Also a Flower. In 2006 Wallach appeared on NBC’s Studio 60 on the Sunset Strip, playing a former writer who was blacklisted in the 1950s. His character was a writer on The Philco Comedy Hour, a show that aired on a fictional NBS network. This is a reference to The Philco Television Playhouse, in several episodes of which Wallach actually appeared in 1955. Wallach earned a 2007 Emmy nomination for his work on the show.  During the filming of The Good, the Bad and the Ugly, Wallach nearly died three times. Once, he accidentally drank a bottle of acid which was placed next to his pop bottle; another time was in a scene where he was about to be hanged, someone fired a pistol which caused the horse underneath him to bolt and run a mile with his hands still tied behind his back; in a different scene with him lying on a railroad track, he was close to being decapitated by steps jutting out from the train.

Wallach appeared as DC Comics’ supervillain Mr. Freeze in the 1960s Batman television series. He said that he received more fan mail about his role as Mr. Freeze than about all of his other roles combined. In 1987 at the age of 71, Wallach starred alongside Michael Landon in Highway to Heaven episode ” A Fathers Faith”.  On November 13, 2010, at the age of 94, Wallach received an Academy Honorary Award for his contribution to the film industry from the Academy of Motion Picture Arts and Sciences. A few years prior to that event, Kate Winslet told another audience that Wallach, with whom she acted in The Holiday in 2006, was one of the “most charismatic men” she’d met.

Eli Wallach was married to stage actress Anne Jackson (born 1926) from March 5, 1948, until his death. They had three children: Peter (born 1951), Roberta (born 1955), and Katherine (born 1958). Roberta played a mentally disturbed teenager in Paul Zindel’s The Effect of Gamma Rays on Man-in-the-Moon Marigolds and appeared in several other movies.  Because Wallach was a strict teetotaler, he once had to ask director John Huston for advice on how to play a “drunk” scene during the filming of The Misfits.  Wallach lost sight in his left eye as the result of a stroke.  His niece is the historian Joan Wallach Scott (the daughter of his brother, Sam Wallach). A. O. Scott, a film critic for The New York Times, is his great-nephew.  Wallach died on June 24, 2014, in New York, at the age of 98. He was survived by his wife of 66 years, three children, three grandchildren and a great-grandchild.