Lewis Allen was born in the small Shropshire town of Oakengates and on leaving school joined the Merchant Navy for four years. After leaving the service he became, briefly, an actor, before moving into London theatrical management, first for Raymond Massey and later for Gilbert Miller. In 1935 he began working on Broadway. His credits include directing the U.S. premieres of Laburnum Grove (1935) and The Amazing Dr. Clitterhouse (1937), and the general stage direction of Victoria Regina, Tovarich and French Without Tears. He directed a wartime propaganda short Freedom Comes High in 1943 and was given his first chance to direct a feature film in 1944. He made a highly auspicious debut with The Uninvited, an atmospheric and memorable ghost story set on the misty coast of south-west England, starring Ray Milland and Gail Russell. The film was very favourably received and subsequently acquired the status of a classic of its genre. Allen again worked with Russell, alongside Joel McCrea and Herbert Marshall, in 1945’s The Unseen, a film with a similar supernatural theme which is often considered the unofficial follow-up to The Uninvited. Other films of this period included a romantic comedy The Perfect Marriage (1947) with David Niven and Loretta Young, and Desert Fury (1947), a noir-ish Western drama starring Lizabeth Scott and John Hodiak.

In 1948 Lewis Allen returned to Britain to film So Evil My Love, a lavishly-mounted melodramatic period thriller set in Victorian London, which reunited him with Milland, playing an out-and-out bad lot ruining the lives of Ann Todd and Geraldine Fitzgerald. Allen later said that he found Milland a pleasure to work with, and the two teamed up again in Sealed Verdict (1948), a topical drama dealing with the prosecution of Nazi war criminals in the American-occupied zone of post-war Germany. The early 1950s brought the biopic Valentino (1951) and the noir Appointment with Danger (1951) starring Alan Ladd, then in 1954 he directed the tense and claustrophobic Frank Sinatra vehicle Suddenly which became, alongside The Uninvited, his most widely known and highly regarded film. In 1955 Allen directed two Edward G. Robinson films, A Bullet for Joey and Illegal. He directed the DuMont television series Ethel Barrymore Theater, filmed in 1953 and shown in syndication as Stage 8 in 1958.

Lewis Allen made only two more films, both in Europe. In Britain, he directed Sean Connery and Lana Turner in the soapy melodrama Another Time, Another Place (1958), while his last was Whirlpool (fr) (1959), a woman-on-the-run drama made for the Rank Organisation but filmed on location in Germany. As his film career began to fade out, Allen made the transition to television, where his services turned out to be in demand from the mid-1950s up to the latter part of the 1970s. His many credits included episodes of hit shows such as Perry Mason, The F.B.I and Mission: Impossible. Most notably, he directed 42 episodes of long-running series Bonanza, spanning the show’s entire 14-year run. He retired in 1977. Allen was married twice: to English literary agent Dorothy Skinner (died 1969 – one son) and Trudy Colmar, who survived him. Lewis Allen died in Santa Monica, California on 3 May 2000, aged 94.