Sharpton's supporters praise "his ability and willingness to defy the power structure that is seen as the cause of their suffering" and consider him "a man who is willing to tell it like it is". Former New York Mayor Ed Koch, a one-time foe, said that Sharpton deserves the respect he enjoys among African-Americans: "He is willing to go to jail for them, and he is there when they need him."

His critics describe him as "a political radical who is to blame, in part, for the deterioration of race relations". Sociologist Orlando Patterson has referred to him as a racial arsonist, while liberal columnist Derrick Z. Jackson has called him the black equivalent of Richard Nixon and Pat Robertson. Sharpton sees much of the criticism as a sign of his effectiveness. "In many ways, what they consider criticism is complimenting my job," he said. "An activist’s job is to make public civil rights issues until there can be a climate for change."

Alfred Charles Sharpton Jr. was born in Brooklyn, New York, to Alfred Charles Sharpton, Sr. and Ada Sharpton. He preached his first sermon at the age of four and toured with gospel singer Mahalia Jackson.

In 1963, Sharpton's father left his wife to have a relationship with Sharpton's half-sister. Ada Sharpton took a job as a maid, but her income was so low that the family qualified for welfare and had to move from middle class Hollis, Queens, to the public housing projects in the Brownsville neighborhood of Brooklyn.

Sharpton graduated from Samuel J. Tilden High School in Brooklyn, and attended Brooklyn College, dropping out after two years in 1975. He became a tour manager for James Brown in 1971, where he met his future wife, Kathy Jordan, who was a backup singer. Sharpton and Jordan married in 1980. The couple separated in 2004.

Sharpton was licensed and ordained a Pentecostal minister by Bishop F.D. Washington at the age of nine or ten. After Bishop Washington's death in the late 1980s, Sharpton became a Baptist. He was re-baptized as a member of the Bethany Baptist Church in 1994 by the Reverend William Jones and became a Baptist minister.

During 2007, Sharpton participated in a public debate with Christopher Hitchens, who is an atheist, and Sharpton defended his religious faith and his belief in the existence of God.

On January 12, 1991, Sharpton escaped serious injury when he was stabbed in the chest by Michael Riccardi while Sharpton was preparing to lead a protest through Bensonhurst, Brooklyn, New York. The intoxicated attacker was apprehended by Sharpton's aides and handed over to police who were present for the planned protest. Sharpton, although forgiving his attacker and pleading for leniency on his behalf, filed suit against New York City alleging that the many police present had failed to protect him from his attacker. In December 2003 he finally reached a $200,000 settlement with the city just as jury selection was about to start.

In February 2007, genealogists using the website Ancestry.com discovered that Sharpton's great-grandfather, Coleman Sharpton, was a slave owned by Julia Thurmond, whose grandfather was Strom Thurmond's great-great-grandfather. Coleman Sharpton was later freed during the Civil War.

Thurmond was notable as the longest serving Senator (at the time of his death) who was a major advocate of racial segregation during the middle of the twentieth century. Thurmond's illegitimate daughter, Essie Mae Washington-Williams, stated she would welcome Sharpton to the family if a DNA test shows he is a relative. In an interview, Sharpton said he has no plans for the DNA test to see if he is related.