On January 30, 2019, Leonardo was loaned to D.C. United from Boca Juniors. He officially debuted for DC on March 3, 2019, in a game against Atlanta United FC. Leonardo typically played as right-back for United. Leonardo scored his first goal for D.C. against the New England Revolution on July 12, 2019, from a volley from Paul Arriola. D.C. United did not sign Leonardo after his loan expired following the 2019 season.