Walter Rilla was born on 22 August 1894 in Neunkirchen/Saar. He was the older brother of the renowned journalist and literary scholar Paul Rilla (1896-1954). Walter Rilla studied literature, art history and philosophy in Breslau, Lausanne and Berlin. In 1919, he founded the literary magazine "Erde" in Berlin; at that time he was temporarily politically active, at first for the KPD (Communist Party of Germany), then for the KAPD (Communist Workers' Party of Germany), a split from the KPD.

From 1920 he worked as a dramaturge for various theatres in Berlin, a little later he began to work as a theatre actor. He made his cinema debut as an angel of death in Urban Gad's classic "Hanneles Himmelfahrt" (1922). Starring in important supporting roles in films like F. W. Murnau's "Die Finanzen des Großherzogs" ("Finances of the Grand Duke", 1924) and Paul Czinner's "Der Geiger von Florenz" ("The Violinist of Florence", 1926), he soon became a demanded character actor, also in leading roles. Among his most important films until 1933 are the period film "Hoheit tanzt Walzer" (1926), the comedy "Prinzessin Olala" ("Art of Love", 1928) with Marlene Dietrich, the social drama critical of the justice system "§173 St.G.B. Blutschande" (1929) and the love drama "Leichtsinnige Jugend" (1931).

After the Nazis seized power, Rilla, who was married to the Jewish Theresa Klausner, only took part in a few German productions, among them Carl Behr's "Der Jäger aus Kurpfalz" (1933) and Heinz Hilpert's contemporary adaptation of Oscar Wilde's "Lady Windermeres Fächer" ("Lady Windermere's Fan", 1935). Instead, he shot the musical comedy "Abenteuer am Lido" (1933, directed by Richard Oswald) in Austria and in 1934 took on a supporting role as brother of the main character in the British production "The Scarlet Pimpernel" ("Die scharlachrote Blume").

In 1935, Rilla finally emigrated to Great Britain with his family; in 1940 he became a British citizen. His wife died in exile in 1948. In England, Rilla starred in supporting roles in numerous film productions, often portraying noblemen or high-ranking military. He played Prince Ernst in "Victoria the Great" ("Königin Viktoria", 1937) and its sequel "Sixty Glorious Years" (1938), and a French commander in the adventure film "Hell's Cargo" (1939) to name only a few. Similar to Conrad Veidt and Peter van Eyck, in exile he also often had to play the villain, be it a Nazi in "The Adventures of Tartu" (1943) and "Lisbon Story" (1946), a gangster in "Golden Salamander" ("Der goldene Salamander", 1950) or an Eastern European potentate in the espionage thriller "State Secret" ("Staatsgeheimnis", 1950). With the drama "Behold the Man!" (1951) Rilla also made his directing debut in England.

In 1956 Walter Rilla returned to Germany; his son Wolf (1920-2005) stayed in England and made a career as a film director. Back in Germany, Rilla got his first role from Kurt Hoffmann: as Lord Kilmarnock in "Bekenntnisse des Hochstaplers Felix Krull" ("Confessions of Felix Krull", 1957). Until 1977 he took part in 30 further film productions, mostly appearing in bigger and smaller supporting roles. The most notable among them are the diabolic Prof. Pohland/Dr. Mabuse in "Das Testament des Dr. Mabuse" ("The Testament of Dr. Mabuse", 1962), "Scotland Yard jagt Dr. Mabuse" ("Dr. Mabuse vs. Scotland Yard", 1962) and "Die Todesstrahlen des Dr. Mabuse" ("The Death Ray of Dr. Mabuse", DE/FR/IT 1964).

Further important films were the Edgar Wallace adaptations "Der Fälscher von London" ("The Forger of London", 1961) and "Zimmer 13" ("Room 13", 1964), the adventure film "Ich, Dr. Fu Man Chu" ("The Face of Fu Manchu", GB/DE 1965), the Italo-Western "Der Tod ritt dienstags" ("Day of Anger", IT/DE 1967) and Rudolf Thome's Munich crime novel "Detektive" (1968). In 1966, Walter Rilla was awarded the German Film Prize for "Many years of outstanding work in German film". He had his last roles in Jess Franco's idiosyncratic Edgar Wallace adaptation "Der Teufel kam aus Akasawa" ("The Devil Came from Akasava", DE/ES 1971) and the horror film "Malpertuis - Geisterschloss des Todes" ("Malpertuis: The Legend of Doom House", FR/BE/DE 1972), playing alongside Orson Welles.

In addition to his cinematic work, Rilla also appeared in numerous television productions. The spectrum ranged from judicial dramas like "Die zwölf Geschworenen" (1963) to literary adaptations like "Die Reisegesellschaft" (1968) based on Guy de Maupassant’s short story "Boule de Suif". Between 1959 and 1969 he also directed some TV films. His last movie role was a small part in "Unordnung und frühes Leid" ("Disorder and Early Torment", 1977) directed by Franz Seitz. Apart from that, in the 1970s he starred in television productions almost exclusively. On 21 November 1980 Walter Rilla died in Rosenheim.