Antonina Leśniewska was born in Warsaw in 1866, the daughter of Bolesław Leśniewski, a doctor, and Michalina née Szeluto.
In order to start an apprenticeship in a pharmacy, she first had to supplement her education with a Latin course, which was lacking in the programs of girls' school.
After completing her compulsory internship, Leśniewska tried to get permission to start her studies, but the authorities of the University of St. Petersburg agreed to it only after a few months.
Despite being accepted, she was not allowed to use the university's laboratories and had to find a room that was hardly visible to outsiders, where she could conduct classes, and she had to attend lectures and demonstrations in physics individually.
In 1921 she founded a children's orphanage in Stara Miłosno near Warsaw (later taken over by the Anti-Tuberculosis School League and transformed into a sanatorium).
In 1933 she returned to the profession of a pharmacist and opened a pharmacy on Marszałkowska Street in Warsaw on the basis of a concession.
She described her experiences in paving the way for women to become pharmacists in her memoirs Po neprotorennoj doroge (The Unpaved Trail), published in St. Petersburg in 1901.