A prolific cartoonist and reporter, Harrington was an outspoken critic of racism in the United States. Langston Hughes called him "America's greatest African-American cartoonist." A New Yorker who immersed himself in the Harlem Renaissance, Harrington worked for the Amsterdam News, creating Dark Laughter, a regular single-panel cartoon later renamed Bootsie after its main character. He studied Fine Arts at Yale University but was unable to finish due to the start of World War II. During the war he produced the comic strip Jive Gray, which featured the adventures of an African-American aviator, and Harrington was sent to Europe and North Africa as a correspondent for the Pittsburgh Courier. After the war, he was hired to develop the public relations department of the NAACP. He published "Terror in Tennessee: The Truth about the Columbia Outrages," a powerful expose of racist police violence that erupted in Tennessee in February 1946.
Harrington's outspoken work against racism attracted government scrutiny, and he moved to Paris in 1951, where he joined a thriving community of African-American expatriate artists and writers including Richard Wright. Wright became a good friend, and his death in 1960 deeply troubled Harrington, who then requested political asylum in East Germany, where he lived out the rest of his life.
