The World Series champion Dodgers continued their stellar year, but it still might not be enough to match the San Francisco Giants, who remain two games ahead in the NL West.
Seager and Trea Turner both hit their 100th career home runs.
Seager reached the mark with his second homer, a drive estimated at 464 feet in the third inning that landed deep in the seats and gave the Dodgers a 3-0 lead.
The Dodgers won 16 of 19 games against the D-backs this season. Kenley Jansen earned his 36th save.
Urías (19-3) is the only pitcher in baseball with a chance to earn 20 wins this year, provided he gets one more start next weekend against the Milwaukee Brewers. The left-hander scattered five hits over five scoreless innings, striking out three and walking one.
Seager and Trea Turner hit solo homers on back-to-back pitches in the first inning for a 2-0 lead off Humberto Mejia. Turner's was especially well-struck, coming off the bat at 108.5 mph and traveling 418 feet.
Mejia (0-3) gave up three runs, all on the three homers. He lasted just 2 2/3 innings, giving up four hits, walking three and striking out one.
The Diamondbacks fell to 50-106. They need at least two wins over their final six games to avoid matching or setting the record for worst season in franchise history. Arizona was 51-111 in 2004.
Seager and Turner became the first set of teammates to hit their 100th homer in the same game since Jay Gibbons and Melvin Mora did it for Baltimore in 2005, according to baseball-reference.com.
It was Seager's ninth career multihomer game.
The Dodgers called up LHP Andrew Vasquez to the big leagues and sent OF Luke Raley to the minors.
Diamondbacks: SS Nick Ahmed was placed on the 10-day injured list with right shoulder inflammation, which will end his season. Arizona called up SS Geraldo Perdomo to take his spot on the roster. Perdomo started on Sunday. The 31-year-old Ahmed had a disappointing year — particularly at the plate — batting .221 with five homers over 129 games.
The Dodgers have Monday off before host a three-game series against the San Diego Padres. RHP Walker Buehler (14-4, 2.58) will start Tuesday's opener for Los Angeles.
The Diamondbacks have Monday off before traveling to San Francisco for a three-game series against the Giants. Arizona will start RHP Luke Weaver (3-6, 4.38) in the opener on Tuesday.