Ernst Unknown studied at school No. 16 in Sverdlovsk and was friends with Vladimir Vinnichevsky during his school years. From 1939 to 1942, he participated in All-Union children's creativity competitions. In 1942, he entered the Secondary Art School under V. A. K. in Leningrad, but in 1941 and 1944, the school was evacuated to Samarkand.

In August 1942, Unknown was drafted into the Red Army and began training at the 1st Turkestan Machine Gun Military School in Kushka, Turkmenistan. After graduating in October 1943, he was sent to the active army with the rank of junior lieutenant to the 4th Ukrainian Front. On March 14, 1944, he was appointed commander of a rifle platoon of the 260th Guards Rifle Regiment of the 86th Guards Rifle Division of the 5th Shock Army. As part of the division, he participated in combat operations of the 2nd and 3rd Ukrainian Fronts, including the assault on Budapest. At the end of the war, on April 22, 1945, in Austria, he was seriously wounded and declared dead, but later awarded the Order of the Red Star and the Medal for Courage. After the injury, he walked on crutches for three years and struggled with severe pain.

For some time, he taught drawing at the Sverdlovsk Infantry School. In 1946 and 1947, he studied at the Academy of Arts of the Latvian SSR in Riga, and then, from 1947 to 1954, at the Moscow State Academic Art Institute named after V. I. Surikov. He also attended courses at the Philosophy Faculty of Moscow State University. In 1955, he became a member of the sculptors' section of the Moscow branch of the Union of Artists of the USSR, but was expelled in 1962 and continued to engage in art in the USSR until 1976.

On June 17, 1973, Unknown submitted documents to emigrate to Israel. On March 10, 1976, after three years as a refusenik, he left the Soviet Union and emigrated to the USA via Switzerland.

Since 1977, Ernst Unknown lived in New York and worked at Columbia University. He celebrated his 80th anniversary in Russia.

In 1996, he was a cultural advisor to Russian President Boris Yeltsin.

In his last years, Unknown was seriously ill and underwent brain surgery. There are two versions regarding his final years. According to one, voiced by his nephew Andrey Rylov, the sculptor's wife Anna Graham treated her husband poorly and expelled his daughter Olga from their home. According to another version presented by Tamara Labadze, Anna took care of her husband.

Ernst Unknown passed away in New York on August 9, 2016, at the age of 92. The funeral service was held at St. Nicholas Cathedral in Manhattan, and he was buried on Shelter Island in the USA.

According to his widow Anna Graham, at the time of his death, their bank account had $3,500. She claimed to have sold her parents' apartment and a portrait of her mother to arrange a funeral costing $300,000. Nephew Rylov stated that Graham sold Unknown's works for personal gain.