Top-ranked Johnson pulled away for his third victory of the season and 19th on the PGA Tour.
Johnson began the day in a four-way tie for the lead, and was dominant from the outset, making back to back birdies on his opening two holes to move ahead of the field.
Using his competitive advantage north of the border, Dustin Johnson, who is married to Paulina Gretzky, the daughter of 'The Great One, ' won the RBC Canadian Open this past weekend behind no shortage of fan support from the Canadian crowd. "I had a lot of support this week".
South Koreans Whee Kim and Byeong Hun An, who were tied for the lead with Johnson and Kevin Tway entering the final round, finished tied for second place after both recorded 69s on Sunday.
"That's the goal for me the last couple years, getting to East Lake and kind of secure my chance at playing in all four majors", he said. "And I normally don't skull over the green, and I skulled over the green, made a 6 there, and I was 2-under in a good spot going into the back nine". "For me to come out and play really solid, play the way I did, I'm very proud of that and I'm very pleased with the win". "I definitely feel like an honorary Canadian". But I felt like I hit the ball plenty good enough to be under par after two days, and I was 5 over or something. He said Saturday he would need to play the par 5s better if he wanted to hoist the trophy and on Sunday he birdied all four.
Kim and An each shot 69 in the round interrupted by a almost 2-hour lightning delay.
After wrapping up a bogey-free 66 on Friday, Johnson picked up where he left off by jump-starting his third round with three consecutive birdies.
But Johnson was able get back on track with birdies at the 14th and 15th before rolling in a 23-foot putt at the 16th for an eagle.
Tway had a 76 to drop into a tie for 17th at 13 under.
LPGA: Ariya Jutanugarn won the Ladies Scottish Open to return to No. 1 in the world ranking, shooting a 5-under 66 for a one-stroke victory over Minjee Lee.
A regular on the Web.com Tour, the 33-year-old showed he can compete with the big guns at Glen Abbey, finishing T-22 on the overall leaderboard - and second among Canucks - with a four-day tally of 12-under 276.
PGA Tour Champions: Miguel Angel Jimenez became the first Spaniard to win the Senior British Open, edging defending champion Bernhard Langer by one shot at St. Andrews, Scotland.
"Winning here definitely means a lot", said Johnson, who picks up $1.116 million for his troubles.
Keegan Bradley threw a 64 on the board to finish at 19 under par in solo fourth and Abraham Ancer carded a Sunday 67 to snag fifth spot. It is also shifting forward in the PGA Tour's schedule, moving to early June in the week before the U.S. Open.