In 1946 Nikulin attempted to enter VGIK (the All-Union State Institute of Cinema), GITIS (Russian Academy of the Theatre Arts), Shchepkin Drama School, other drama art schools and colleges, but to no effect. Finally he found himself at the clownery school attached to the Moscow Circus on Tsvetnoi Boulevard.
Nikulin fought in the Red Army in the Winter War with Finland and the World War II with Germany. He reportedly had a comparable "long period of military service, from 1939 to 1946, preparing to be demobilized just when the German invasion of the Soviet Union began in 1941.
Nikulin first took up clowning in 1944 when a political officer in his battalion, impressed by his repertoire of jokes, ordered him to organize entertainment for the division, which he did with resounding success. Nikulin, affectionately called Uncle Yury by Russian children, relied mainly upon his wits to earn his place in history as one of the best clowns of the 20th century.
His screen debut came in 1958 with the film The Girl with the Guitar.