After entering the game as a halftime substitution, Yow was in prime position for the late equalizer. A cross into the box was headed by Toronto defender Omar Gonzalez right to D.C. academy product Yow, who delivered a well-placed strike past goalkeeper Quentin Westberg.
It was the first career MLS goal for Yow, who celebrates his 18th birthday later this week.
For Toronto FC, Yow's goal was an unwelcome echo of the previous match between the two clubs this season. Frederic Brillant scored in stoppage time to give D.C. another 2-2 draw on July 13 during the MLS Is Back tournament.
D.C. hadn't scored more than one goal in a game since that first Toronto meeting, a span of eight matches.
Ayo Akinola scored twice in that July 13 game and continued to plague D.C. United on Saturday. In the 60th minute, Pablo Piatti flicked a pass from the far side of the box back in front for Akinola to convert a header for Akinola's sixth goal of the season.
Ola Kamara put D.C. ahead just five minutes into the game, rushing on a near-breakaway after an ugly turnover from Gonzalez near midfield.
It was Kamara's second goal of the season, and a rare early strike from D.C. United. It was the club's first goal scored within the first 58 minutes of any match this season.
Alejandro Pozuelo equalized 12 minutes later, this time capitalizing on something of a miscue from a D.C. player. Defender Donovan Pines made a poor attempt at intercepting a Richie Laryea cross, putting the ball right at Pozuelo's feet for the striker's fourth goal of the season.
The draw brings Toronto FC into third place in the Eastern Conference.