Tilden attended Yale College and the University of the City of New York for brief periods and studied law. He began to practice law in New York City in 1841. Despite frequent illnesses, he soon became a corporation and railroad lawyer of great skill and a leader in Democratic politics. He was a member of the New York Assembly in 1846 and was a member of the state constitutional conventions (1846 and 1867). He was a leader of the Free-Soil element among New York Democrats and supported the Union cause in the American Civil War (1861–65). He played a prominent role in the reorganization of the Democratic Party in the decade from 1865 to 1875, serving as the party chairman of New York state. During this period he played a major role in the overthrow of the notorious Tweed Ring, a circle of corrupt politicians who had defrauded New York City of an estimated $30,000,000–$200,000,000, and in the removal of several corrupt judges. Elected governor (1874) on a reform platform, he won national recognition for his efficient administration and for exposing the Canal Ring, a conspiracy of politicians and contractors engaged in defrauding the state.

Tilden was a distant, secretive, dilatory, and cautious man who possessed marked intellectual ability. His frail health and characteristic indecision forced him into the background of politics after 1877, though he retained great influence in the Democratic Party. His law practice and investments had brought him great wealth, and he left the bulk of his estate in trust for the establishment of a free public library for New York City.