Киевская губерния
Iwaszkiewicz was born in Kalnyk in Kiev Governorate of the Russian Empire (now Vinnytsia Oblast, Ukraine). After the death of his father (an accountant), he and his mother lived in Warsaw in 1902–1904, and then moved back to Kiev Governorate. He graduated from a secondary school in Kiev in 1912 and enrolled at the Law Faculty of Kiev University.