Iakov Fainzilber was born in 1901 in Vasilkov, 20 miles south of Kiev, Ukraine. In 1919 he graduated from a gymnasium in Kiev and entered the Kiev Medical Institute (now Bogomolets National Medical University). Upon completing his studies there in 1925, he worked as a surgeon at various regional medical centers in Ukraine and Belorussia. In the 1930s Fainzilber returned to Kiev, where he specialized in neurosurgery. By the time the Soviet-German war began in June 1941, he had published five scientific works.
Iakov Fainzilber was drafted into the Red Army in 1939 and, as a military doctor, took part in the Soviet invasion of Eastern Poland in September 1939. In 1940, he was released, but in the summer of 1941, with the German attack on the Soviet Union, he was called up for service again. He began as an ordinary neurosurgeon in a military hospital deep in the rear, but from 1942 he headed the neurosurgery departments at various rear hospitals attached to the Leningrad Front, the 3rd Baltic Front, the 2nd Belorussian Front, and other fronts. In December 1942 and in 1943, on the 3rd Baltic Front Fainzilber performed 1,210 operations on the brains, spinal cords, and peripheral nervous systems of the wounded. His highest rank during the war was major of the medical service. He was awarded three military orders and medals.
In December 1943, an article on Iakov Fainzilber was prepared for the Moscow-based Yiddish newspaper Eynikayt by Mikhail Tsunts.
After the war, Fainzilber returned to medical science. In 1947 he defended his dissertation ("The surgical treatment of gunshot wounds of the spine and spinal cord") and, subsequently, headed the department for acute trauma of the central nervous system at the Kiev Psycho-neurological Institute. He died in 1973.