Educated in the Warsaw cadet corps between 1770 and 1777, Niemcewicz spent most of the period 1783–88 in western Europe and in 1788 was elected deputy to the Sejm (parliament) of Poland. In 1790 he wrote Powrót posła (“The Deputy's Return”), a political comedy very popular in its day. After participating in the unsuccessful insurrection against Russia of 1794, when he served as an aide-de-camp to Tadeusz Kościuszko (Kościuszko, Tadeusz), he was captured at Maciejowice and imprisoned in St. Petersburg for two years. Upon his release, he traveled to England and then with Kościuszko to the United States, where he met George Washington, Thomas Jefferson, and other American political leaders. He married in the United States and remained there until 1807, when he returned to Poland. His recollections of that period—Podróże po Ameryce 1797–1807—have been translated into English and edited by Metchie J.E. Budka and published as Under Their Vine and Fig Tree: Travels Through America in 1797–1799, 1805, with Some Further Account of Life in New Jersey (1965).

While Niemcewicz strove to add a moderate voice to the social and political unrest in Poland between 1807 and 1831, he devoted himself primarily to literary work, publishing Śpiewy historyczne (1816; “Historical Songs”), a series of simple song poems that became very popular, and Lebje i Sióra (1821; Levi and Sarah, or, The Jewish Lovers: A Polish Tale), the first Polish novel to discuss the problems of Jews in Polish society. In 1831 he journeyed to England to attempt to persuade the western European powers to intervene on behalf of the Polish insurrection against the Russians. He failed to do so, however, and spent the last years of his life in Paris, campaigning for Polish freedom. His memoirs appeared in 1848.