Zakrzewska was born in Berlin, the eldest of six children to Ludwig Martin Zakrzewski and Caroline Fredericke Wilhelmina Urban. Her father was from a noble Polish family which had lost its wealth and property to the Russians, so he worked as a civil servant. Her grandmother was a veterinary surgeon, and her mother worked as a midwife.
She also broke barriers that hindered women in practicing medicine in the United States, founded hospitals for women, and pioneered the movement that opened the nursing profession to black women with the first black nurse in America graduating from the school in 1879. As a feminist and abolitionist, she became friends with William Lloyd Garrison, Wendell Phillips and Karl Heinzen.