The U-20 women are U.S. Soccer's only age-group program that has advanced to every world championship.
Goals from 17-year-old midfielders Jasmine Aikey and Lauren Martinho gave the USA a 2-0 lead after 48 minutes, but it struggled to put away the Ticas despite a huge edge in shots (19-1 in the first half and 29-6 overall).
Costa Rica made the match close when Sheika Scott converted a penalty kick in the 55th minute to make it 2-1.
In stoppage time, the USA was reduced to 10 players when defender Gisele Thompson was sent off for a DOGSO foul. On the ensuing free kick, Mariana Solano hit the crossbar.
Next up: The USA will face Mexico, a 2-1 winner over Canada in the other semifinal, in Sunday's final. It has advanced to every Concacaf U-20 final, winning seven times. It was the runner-up to Canada twice (2004 and 2008) and Mexico once (2018).
June 2 Santo Domingo
USA 2 Costa Rica 1. Goals: Jasmine Aikey 38, Martinho 48; Scott 55 pen.
USA -- Wy; Thompson, Evans, Klenke, King; Aikey, Flammia (Lemos, 67), Martinho; Gamero (Dudley, 76), Sentnor (Dellarose, 90+5), Dahlien.
Costa Rica -- Perez; Rivera, Mena (A.Gonzalez 64), Benavides (Rodriguez, 10), Briceno, Vasquez; Matarrita (T.Fonseca, 82), Jimenez, L.Gonzalez (Aguero, 64), Diaz (Solano, 64); Scott
Yellow Card: Costa Rica -- Briceno 45+7. Red Card: USA -- Thompson 90+3.
Referee: Sandra Benefitz (El Salvador). ARs: Lidia Ayala (El Salvador), Ivett Santiago (Cuba). 4th Official: Odette Hamilton (Jamaica). VAR: Ismael Cornejo (El Salvador). AVAR1: Francia Gonzalez (Mexico).