The daughter of a musician, she married an actor, Gustav Modrzejewski, and they joined a company of strolling players. In 1868 she married Count Bozenta Chlapowski, a politician and critic, and began to act at Warsaw, where she remained for a number of years.

Her chief tragic roles were Shakespeare's Ophelia, Juliet, Desdemona, and Queen Anne in Richard III, Schiller's Princess Eboli, Victor Hugo's Tisbé, and Juliusz Słowacki's Mazeppa. In comedy her favourite roles included Beatrice in Much Ado About Nothing. Modjeska also played in modern pieces by Gabriel Legouvé, Dumas (father and son), Guillaume Augier, Alfred de Musset, Octave Feuillet, and Victorien Sardou.

In 1876 she went with her husband to California, where they settled on a ranch. This enterprise was a failure, and Modjeska returned to the stage. She appeared in San Francisco in 1877, in an English version of Adrienne Lecouvreur, in which she was very successful despite her poor English. She continued to act principally in the United States but was also seen from time to time in London, where in 1881 she fulfilled her ambition to play Shakespeare on an English stage, and elsewhere in the United Kingdom. Her autobiographical Memories and Impressions of Helena Modjeska was published in 1910.