The Raptors had a three-point lead entering the fourth quarter and built it to nine.
When the Wizards moved to within five, Raptors reserve guard Fred VanVleet made a 3-pointer with 1:15 to play.
C.J. Miles added 12 points for the Raptors (11-5), who have won four in a row. Kyle Lowry and VanVleet each added 10 points for Toronto.
Bradley Beal led Washington (9-7) with 27 points while Otto Porter Jr. added 15. Marcin Gortat had 12 points and grabbed 12 rebounds for the Wizards.
The Wizards were playing without guard John Wall, who has a swollen left knee.
It was the second game Wall has missed this season at the Air Canada Centre. He also was out with a sprained left shoulder when the Wizards defeated the Raptors.
Sunday's game was tied at 18 after the first quarter. Beal led all scorers with 12 points.
The Raptors led by as many as eight points during the second quarter and took a 60-55 lead into the intermission.
Beal had 23 points in the first half and DeRozan had 22.
Beal's 3-pointer with 8:43 left in the third quarter tied the game at 64.
Porter's 3-pointer put the Wizards into a three-point lead slightly more than a minute later.
Miles hit a 3-pointer with 4:28 left in the third and Toronto led by four.
The Raptors led 79-76 after three quarters.
The Raptors led by six with 8:10 remaining in the fourth quarter after Miles was fouled while hitting a 3-pointer. He converted the free throw to complete the four-point play.
Pascal Siakam's short bank shot gave Toronto a nine-point lead with 6:17 left.
After the lead was cut to five DeRozan made a 3-pointer.
NOTES: Raptors G Norman Powell (right hip pointer) missed his fourth straight game on Sunday. ... Toronto G Delon Wright (dislocated right shoulder) missed his second game in a row and will be examined by a specialist in New York this week. ... Raptors F Serge Ibaka (swollen left knee) returned to the lineup Sunday after missing the game Friday. ... Wizards PG John Wall (swollen left knee) did not play Sunday, but Washington coach Scott Brooks said there is a good chance that he could play Monday when the team visits Milwaukee to play the Bucks. PG Tim Frazier replaced Wall in the starting lineup and had six points, eight assists and eight rebounds. ... The Raptors will visit the New York Knicks on Wednesday.