With the win, Johnson extended his career-long season victory streak to 13. He hadn't won since last year's WGC-Mexico Championship.
"I'm definitely proud of myself for continuing the streak, and I want to keep it going," Johnson said. "It was a long time between wins, though, and so hopefully it won't be that long for the next one."
Johnson finished at 19-under 261 for his 21st PGA Tour win, just one stroke ahead of Streelman (67) and two ahead of Will Gordon (64) and Mackenzie Hughes (67).
Gordon, who has no status on either the PGA Tour or the developmental Korn Ferry Tour, recorded seven birdies in his fourth-round 64. His third-place finish was enough to earn him a special temporary card and unlimited exceptions for the remainder of the season.
Bryson DeChambeau shot a 68 to tie for sixth at 15-under, while top-ranked Rory McIlroy tied for 11th at 13-under after his 67 on the final round. Jordan Spieth (69) ended in a tie for 54th at 6-under 274.
Phil Mickelson -- playing in his first tournament since turning 50 less than two weeks ago -- followed up his first two rounds of 64 and 63 with two 71s to finish in a tie for 24th at 11-under. He led the field Friday after recording his best score in a PGA Tour tournament since 2018.
"I'm looking at this week as progress," Mickelson said. "Certainly, the goal is to win golf tournaments, but keep in mind I've missed a bunch of cuts. I haven't played to the level I've wanted to, and this week I came in and had a lot of great finds. I hit a lot of good shots, hit a lot of good tee shots. My misses were much better."
There were seven players who withdrew from the Travelers Championship because of the coronavirus. Two players -- Cameron Champ on Tuesday and Denny McCarthy on Friday -- tested positive for the virus.
The PGA Tour announced it will make multiple changes to its COVID-19 policies as a result of this week's testing results. Players, caddies and any other personnel "inside the bubble" will be required to test negative before being allowed on the grounds of the Detroit Golf Club for this week's Rocket Mortgage Classic.