Dallas outscored Real Salt Lake 3-2 in the two-game aggregate-goal series. Substitute Robbie Findley scored in the 79th minute for Real Salt Lake. Five minutes earlier, Findley put a point-blank header off the crossbar.
Dallas will play Los Angeles or Seattle in the Western Conference finals.
David Ferreira laid a long pass ahead to Brek Shea, who started for the first time since Sept. 15. Shea chested the bouncing ball to McCarty, who beat keeper Nick Rimando.
Real Salt Lake played without Javier Morales, who received a second yellow card in the second half of the first game.
FC Dallas played without Atiba Harris, sent off late in the first match.