The result sends the Pumas through to a second-round match against Sounders 2 next Wednesday at Starfire Stadium in Tukwila.
Kitsap jumped ahead in the fourth minute, increased it to 3-0 by halftime, and eventually to 5-0. The Pumas got two goals each from Joe Masumiya and Carlos Patino and one from Jake Bond.
Tacoma got on the board with a close-range goal from Steven Wright in the 76th minute and a 20-yard free kick from Pedro Millan in the 88th.
Tacoma 253 was formed in January as a member of the National Premier Soccer League, while Kitsap is an established Premier Development League power and defending Western Conference champion.
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Seattle Sounders FC and other Major League Soccer teams join the tournament in the fourth round at the middle of June.
Final: Kitsap 5, Tacoma 2. Pumas will meet Sounders 2 a week from tonight at Starfire in second round of the U.S. Open Cup.
88' GOAL Tacoma. 20-yard free kick -- quality at any level -- from Pedro Millan. Kitsap, 5-2.
76' GOAL Tacoma. Steven Wright gets 253 on the board from close in front of goal. Kitsap, 5-1.
Attendance: Estimated at 300.
54' GOAL Kitsap. Patino with his second. Pumas, 5-0.
48' GOAL Kitsap. Jake Bond finishing a corner kick. Pumas, 4-0.
HT: Kitsap 3, Tacoma 0. #USOC2015 Pumas dominating, but not as one-sided as score. They have finished, while 253 hasn't.
39' GOAL Kitsap. Long pass to Masumiya, who gets second goal of game. Pumas, 3-0.
34' GOAL Kitsap. Nice through ball by Ramos for second assist. Carlos Patino jukes charging keeper and finishes into emty net. Pumas, 2-0.
4' Joe Masumiya puts Kitsap ahead early, 1-0, after cross from Mike Ramos.
Pregame: It's FC Tacoma 253 hosting the Kitsap Pumas tonight at Mount Tahoma Stadium, in the first round of the U.S. Open Cup.
The winner goes on to meet Sounders 2 next Wednesday at Starfire.