"We have received several threats that we consider serious," Sharpton told the Daily News in Sunday's edition. "I have been stabbed once, so we don't take anything too lightly."
Sharpton was stabbed in the chest in 1991 during a protest in Brooklyn.
Charlie King, acting executive director of Sharpton's National Action Network, said a caller telephoned the civil rights leader's radio show on Saturday and threatened to "hunt him down and shoot him like an animal."
Police confirmed they have an increased presence near Sharpton's church in Harlem and his staff.
Sharpton became one of Imus' most vocal critics after the shock jock used a racial slur while referring to the Rutgers women's basketball team. Imus was fired from his radio show after calling the team "nappy-headed hos."