Tie games have been a common occurrence of late for Nashville SC (11-3-15, 48 points), who have tied four straight matches to reside two points above third-place Philadelphia in the Eastern Conference. The Union settled for a 2-2 tie against CF Montreal earlier Saturday.
Nashville SC now are 2-0-1 in three all-time matches against D.C. United. Nashville posted a 5-2 win over D.C. United on Aug. 15.
Bill Hamid made two saves for D.C. United (12-12-5, 41 points), who have followed a 3-1-0 stretch with a 2-1 loss to Orlando City on Oct. 2 and Saturday's draw. D.C. United are 4-0-1 in their last five home games.
D.C. United nearly opened the scoring twice in the early going.
D.C. United kept the pressure on in the second half, with Russell Canouse's initial shot was blocked by Jack Maher from close range in the 57th minute. Canouse attempted to exact revenge eight minutes later, only to be denied from in close by Willis.
Nashville's best opportunity came in the 82nd minute as Hany Mukhtar's sharp-angle shot from near the end line was denied by Hamid. Mukhtar leads the team with 13 goals on the season.
D.C. United played without Paul Arriola, who sustained a groin injury during warmups with the United States men's national team on Wednesday. Yordy Reyna (calf), Edison Flores (calf) and Brenden Hines-Ike (hip) also were ruled out.
Nashville fullback Dan Lovitz was ruled out for Nashville SC.