In exchange, the Capitals received AHL goalie Jesper Vikman, a 2027 third-round pick, and a 2029 second-round pick.
Dowd, 35, has been with the Capitals the past eight seasons. He has four goals and 12 assists through 55 games this season. He needs 11 more goals and five more assists to set career highs in both with just 20 games left on the Knights' schedule.
Vikman, 23, is 8-7 in net this season for the Henderson Silver Knights, ranking dead last (60th) in the AHL with a .833 save percentage and 5th with a 3.41 goals against average.
Dowd will provide center depth on the fourth line for the Golden Knights. He'll more than likely be paired up with Cole Smith (LW), who was also recently acquired in a trade with the Nashville Predators, and right wing Keegan Kolesar.
The Knights are currently sitting in fourth place in the Western Conference with a 29-19-14 record (72 points) and atop the Pacific Division.
They advanced to round two of the NHL Stanley Cup Playoffs last year after defeating the Minnesota Wild in six games (4-2). They then lost to their division rivals Edmonton Oilers in five games (4-1), effectively ending their season.
As for the Capitals, they're currently on the outside looking in as they're in a massive fight for a Wild Card spot in the competitive Eastern Conference. They currently boast a 31-25-7 record (69 points), sitting four points below the Boston Bruins (73 points) for that second Wild Card spot.