William DeWolf Hopper Jr., was born January 26, 1915 in New York City. He was the only child of actor, singer, Comedian, and theatrical Producer DeWolf Hopper (March 30, 1858 – September 23, 1935) and his fifth wife, Actress Hedda Hopper (born Elda Furry; May 2, 1885 – February 1, 1966). He had one older half-brother, John A. Hopper, from his father's second marriage in the 1880s. Hopper made his film debut as a baby in his father's 1916 silent movie Sunshine Dad. His mother divorced his father in 1922 and moved to Hollywood with their son. Hedda Hopper became one of America's best-known gossip columnists, with nearly 30 million readers in newspapers in the U.S.

Hopper began his acting career as a teenager. He made his first stage appearance at the Pasadena Community Playhouse, in She Loves Me Not. He worked in summer stock in Ogunquit, Maine. He appeared on Broadway in the short-lived comedy Order Please (1934) and as a member of the ensemble in Katharine Cornell's production of Romeo and Juliet (1934–35).

In March 1936, Hopper — then working under the name Wolfe Hopper — won a contract at Paramount Pictures. Early in his film career, Hopper appeared in numerous movies, uncredited and also under the name DeWolf Hopper. In 1936, he played a small role as a soldier in the Columbia Pictures film The King Steps Out starring Grace Moore and Franchot Tone. In 1937, he portrayed the leading man in two films, Public Wedding with Jane Wyman and Over the Goal with June Travis. He also enjoyed significant roles alongside Ann Sheridan in The Footloose Heiress (1937) and Mystery House (1938).

After that, he had roles that included playing a sergeant in the John Ford Western, Stagecoach (1939); an intern in The Return of Dr. X (1939); a college football player in Over the Goal (1939); and reporters in Knute Rockne, All American (1940), The Maltese Falcon (1941) and Yankee Doodle Dandy (1942).

In 1940, Hopper married Actress Jane Kies, whose professional name was Jane Gilbert; she was the sister of Margaret Lindsay. They had worked together on the 1939 film, Invisible Stripes. They had one daughter, Joan, born in 1947.

In 1953, Director william Wellman persuaded Hopper to resume his movie career with his 1954 film, The High and the Mighty, opposite Jan Sterling. Before filming began, Hopper challenged Wellman because he suspected his mother had arranged the offer. "When it appeared Wellman was serious, I asked him if he knew whose son I was. He ignored me," Hopper recalled. "I was so lousy, so nervous, I didn't even know where the camera was. But somehow Billy got me through. Afterward, I thanked him. He said, 'Thank me, my foot. After this, you're going to be in every picture I make.' I didn't believe him." Hopper subsequently appeared in two of Wellman's films, Track of the Cat (1954) and Good-bye, My Lady (1956).

At last comfortable on screen, Hopper played the stern and emotionally distant father of Natalie Wood in the James Dean classic, Rebel Without a Cause (1955), and the often absent father in The Bad Seed (1956). He starred in the science-fiction films 20 Million Miles to Earth and The Deadly Mantis, released in 1957.

In 1956 Hopper guest-starred again on television during the first season of the Western series Gunsmoke, portraying an outlaw initially supported by townsfolk in an episode titled "Robin Hood". The following year he played a supporting role in the pilot episode of the television series The Restless Gun, which was broadcast as an episode of Schlitz Playhouse of Stars. Some of Hopper's other television guest appearances include The Joseph Cotten Show, Fury, Studio 57, and The Millionaire.

Hopper is best known for his principal role as the private investigator Paul Drake on CBS's courtroom television series Perry Mason (1957–66). He initially tested for the title role, while Raymond Burr read for the role of Mason's courtroom adversary, district attorney Hamilton Burger. Burr was encouraged to lose weight and return to audition for the role of Perry Mason — which he later did, successfully. Hopper, too, was called back. Executive Producer Gail Patrick Jackson recalled, "When Bill Hopper came in to read for Paul Drake he blurted out, 'You hate my mother.' And that was Hedda Hopper. Well, I disliked what she stood for, but 'hate' is something else — and anyway he was perfect as Drake, and we got him."

In 1959, Hopper was nominated as Best Supporting Actor (Continuing Character) in a Dramatic Series at the 11th Primetime Emmy Awards for his performance as Paul Drake.

On February 1, 1966, Hopper announced the death of his mother, Actress and celebrated Hollywood columnist Hedda Hopper, from pleural pneumonia.

Hopper entered Desert Hospital in Palm Springs, California, on February 14, 1970, after suffering a stroke. He died of pneumonia three weeks later, on March 6, at age 55. Survived by his second wife, Jan, he was buried in Rose Hills Memorial Park in Whittier, California.