Born in Highspire, Pennsylvania in August 1916, Donald Keefer was the youngest of three sons of Edna (née Hood) and John E. Keefer, who worked as a butcher. When he was in his early 20s, “Don” moved to New York City, where he attended the American Academy of Dramatic Arts, graduating from that prestigious acting school in 1939. That same year, at the New York World’s Fair, he performed various roles on stage in excerpts of works by William Shakespeare. During the 1940s, Keefer found work as supporting characters in Broadway plays such as Junior Miss and Othello. He also began studying method acting in Manhattan as an early member of The Actors Studio. In this period, he gained some early experience and performed in the new medium of television. In 1947, Keefer appeared in a televised presentation of Shakespeare’s play Twelfth Night and in an episode of the anthology series Kraft Television Theatre. The next year, he performed again on Kraft Theatre in an episode titled “The Silver Cord”.

By 1949, Keefer was back on Broadway as a cast member in the acclaimed production of Arthur Miller’s play Death of a Salesman, directed by Elia Kazan. Keefer’s exposure in that play led to his first movie role, reprising his performance as Bernard in the 1951 film version of Death of a Salesman. He soon appeared in other films, including The Girl in White (1952), The Caine Mutiny (1954), Six Bridges to Cross (1955), Away All Boats (1956), and Hellcats of the Navy (1957). Increasingly, however, Keefer in the 1950s began focusing on performing on the “small screen”, accepting more roles in a wide variety of television series.

On May 7, 1950, Keefer married the actress Catherine McLeod, and the couple remained married for 47 years, until her death on May 11, 1997. At the time of Catherine’s death, the Keefers were living in Sherman Oaks in the San Fernando Valley of Los Angeles County, California. The three Keefer sons are Donald McLeod, John H., and Thomas James. Don Keefer died at the age of 98 on September 7, 2014, and his burial was at Woodlawn Cemetery in Santa Monica, California.

Keefer appeared in dozens of television series, including other early anthologies: Fireside Theatre, Armstrong Circle Theatre, The Philco Television Playhouse, the United States Steel Hour, Alcoa Presents: One Step Beyond, The DuPont Show with June Allyson, and Death Valley Days. In 1957, Keefer appeared as McNair in the episode “Ito of Attu” on ABC Navy Log. That same year, he appeared with David Janssen as the character Reagan in “Big Score” of the CBS series Richard Diamond, Private Detective. In 1958, he appeared as Ed Locke in the episode “Wild Green Yonder” of the syndicated crime drama State Trooper, starring Rod Cameron. In 1959, Keefer appeared as John Alastair in the episode “Death Is a Red Rose” of the Craig Stevens NBC crime drama Peter Gunn. Keefer performed in three episodes of CBS’s anthology Alfred Hitchcock Presents: in the role of Dr. Elkins in “The Indestructible Mr. Weems” (1957), as Pete Williams in “The Percentage” (1958), and as a tax clerk in “The Kiss-Off” (1961). He also had small roles in some feature films, including Woody Allen’s Sleeper. In 1966, he played the character Irving Christiansen in the movie The Russians Are Coming, the Russians Are Coming.

Keefer appeared as Cromwell in the 1968 episode “Assignment: Earth” of the NBC science fiction series Star Trek. Earlier, he had roles in the following three episodes of CBS’s The Twilight Zone: as Dan Hollis in “It’s a Good Life” (1961), as Spiereto in “Passage on the Lady Anne” (1963), and as Fred Danziger in “From Agnes – With Love” (1964).

Keefer’s last role was as a beggar at a courthouse in the 1997 film Liar Liar.