The second-year quarterback has played well at times this year but hadn't had a breakout game while dealing with rib and lung injuries over the past few weeks.
The Texans (5-3) have left their 0-3 start behind with their longest single-season winning streak since reeling off six victories in a row in 2012.
"I think we've got the best offense in the NFL," receiver DeAndre Hopkins said. "What we put up tonight against a pretty good defense, what we've shown in these past five games that we've won, we're up there with the best of the best."
Watson threw touchdown passes of 13, 2, 73, 49 and 2 yards to give him 34 career scoring passes, moving ahead of Dan Marino (32) for second-most in NFL history after 15 games.
"This offense can be very explosive," Watson said. "We can do a lot of good things, put a lot of points on the board."
Miami's Brock Osweiler, who had one tough season in Houston after signing a $72 million contract in 2016, threw for 241 yards with an interception in his third straight start in place of injured starter Ryan Tannehill.
Kenyan Drake had a touchdown run and touchdown reception for the Dolphins (4-4). They lost for the second straight week.
"I'm fairly irritated right now," Miami coach Adam Gase said. "I'm going to re-evaluate everything this weekend and figure out how to get better on defense, figure out how to sustain drives and get the ball into the end zone on offense."
Rookie Jordan Thomas caught the first two touchdown passes of his career, Hopkins had 82 yards receiving and two scores, and Will Fuller added 124 yards receiving and a touchdown.
Texans running back Lamar Miller, who grew up in Miami and spent his first four seasons with the Dolphins, had 133 yards rushing and a touchdown for his second straight 100-yard game.
Houston led by eight when Watson threw a 49-yard touchdown pass to Hopkins on the first play of the fourth quarter to make it 35-20.
Watson found the speedy Fuller in front of the defense for a 73-yard touchdown that left Houston up 28-17 late in the third quarter. It was the longest touchdown pass of Watson's career and the longest reception of Fuller's. Fuller has caught 11 touchdown passes in 11 career games with Watson.
The Dolphins used a 41-yard field goal to cut the lead to 28-20 with less than a minute left in the third quarter. That score came after a drive featuring a crazy 46-yard pass by Osweiler . He threw the ball to Jakeem Grant, who lost it after being hit by two Texans defenders, but it sailed down the field and into the hands of DeVante Parker for the big gain.
A 58-yard run by Miller got the Texans to the 9-yard line early in the third quarter. Houston extended the lead to 21-10 when Watson found Thomas again, this time on a 2-yard pass.
The Dolphins used some trickery later in the third quarter when Osweiler pitched a lateral to Danny Amendola, who threw a 28-yard touchdown pass to Drake to cut the lead to 21-17.
Houston CB Johnathan Joseph injured his ankle in the first quarter and didn't return. ... ILB Zach Cunningham left in the first quarter with a knee injury and didn't return. ... Fuller left the game after injuring his knee in the fourth quarter.
THE CATCH THAT WASN'T
Hopkins scored his second touchdown on a 2-yard reception with about eight minutes left in the fourth quarter, but his most impressive play of the night came on a catch that didn't count . Hopkins reached back and grabbed the ball with one hand and weaved it between his legs in the air before crashing to the ground. But it was brought back after he was called for pass interference.
"I knew the guy had my other arm, so I couldn't put my other arm to catch the ball, so I knew I had to pin it up against something just to hold onto it," Hopkins said.
Miami defensive end Robert Quinn again raised his right fist during the anthem as he has done in past weeks.
Dolphins: Host the New York Jets on Nov. 4.
Texans: Visit Denver on Nov. 4.
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