Justin Robinson made a go-ahead jumper with 11 seconds remaining to send No. 12 Miami into a second-round matchup with the unbeaten and fifth-seeded Los Angeles Clippers.
Robinson scored 13 of his 19 points in the fourth quarter as Miami improved to 3-1. Lamond Murray Jr. added 17 points.
Washington, the No. 21 seed, fell to 0-4 despite 18 points from Marcus Keene. Ike Diogu had 15 but his potential winning shot was blocked.