Moris Slobodskoy was born in 1913 in St. Petersburg. His father Ruvin was a native of Vilna. After finishing school, Moris Slobodskoy began to work as a journalist. From the early 1930s, he wrote feuilletons that were published in the popular satirical magazine Krokodil. In 1938, Slobodskoy joined the Soviet Writers' Union.
In late June 1941, immediately after the outbreak of the Soviet-German War, Moris Slobodskoy was dispatched to the front as a special correspondent. There, he wrote feuilletons and short stories for the frontline newspaper Krasnoarmeyskaya Pravda, including chapters from the serial novel The New Adventures of the Good Soldier Schweik. Slobodskoy would go on to write ninety chapters of this novel. The character of Jozef Schweik had originally been conceived by Czech author Jaroslav Hašek, first appearing in print in a short story collection from 1912. He later became the protagonist of a novel, which became popular enough to inspire sequels by other writers.
In the course of the war, Moris Slobodskoy was awarded the Orders of the Red Star and the Patriotic War, 2nd class, and some medals.
In 1945, after the end of the war, Moris Slobodskoy returned to Moscow. He then partnered with the writer Vladimir Dychovichny, and the two went on to collaborate for eighteen years, writing satirical plays, poems, feuilletons, scripts for vaudevilles, and lyrics for some songs that became popular in the USSR.
After Vladimir Dychovichny's death in 1963, Slobodskoy teamed up with Yakov Kostyukovsky. Together, they wrote the scripts for numerous films, including the celebrated comedies Operation Y and Shurik's Other Adventures (1965) , Kidnapping, Caucasian Style (1966), The Diamond Arm (1968), and many others.
Moris Slobodskoy died in Moscow in 1991.