Delany began publication of a black newspaper in Pittsburgh in 1843. This paper suspended publication in 1847, after which Delany briefly worked as co-editor of the North Star in Rochester, New York. In 1850, Delany and two other black men entered Harvard Medical School. Complaints from several white students, who objected to the presence of the three black, soon ended Delany's stay there, however. Delany turned once again to writing and published The Condition, Elevation, Emigration, and Destiny of the Colored People of the United States, Politically Considered in 1852. This book supported the emigration of blacks outside the United States, and Delany himself moved to Chatham, Canada, in 1856.
In 1858, Martin Delany attended John Brown's Chatham Convention, where Brown presented his Provisional Constitution and revealed a plan to free slaves that led to the raid on Harpers Ferry in October 1859. While Brown obtained Delany's support at Chatham, Delany and other prominent blacks, such as Frederick Douglass, distanced themselves from Brown as his actions became more militant and unpredictable.
During the Civil War, Delany recruited black troops in Massachusetts and other New England states. He also became the first black field officer in the Union Army in 1865 when he was commissioned major. After the war, Delany lived for several years in South Carolina. Among his activities, Delany worked for the Freedmen's Bureau for three years and was active in politics. Increasingly unhappy with Reconstruction, Delany eventually gave his support to white Democratic redeemer Wade Hampton.
In addition to The Condition, Elevation, Emigration, and Destiny of the Colored People in the United States, Delany authored a novel Blake, or the Huts of America, Official Report of the Niger Valley Exploration Party, and Principia of Ethnology. He died in Wilberforce, Ohio, on January 24, 1885.