Wang (2-2), making his third start of the season, managed to hold the Blue Jays to two runs over five innings despite his wildness. The right-hander allowed four and struck out five.
Bryce Harper went 3-for-4 with a solo homer while Danny Espinoza added a two-run shot and Jhonatan Solano cracked his first major-league round-tripper as the Nationals took the opener of a three-game series.
Toronto's Henderson Alvarez (3-6) was tagged with the loss, allowing four runs on nine hits over seven frames.
Jose Bautista socked his 18th homer for the Blue Jays.