| 1. Round | 25/03/2018 | Swope Park Rangers | - | Seattle Sounders 2 | 4:2 | ||||
| 3. Round | 06/05/2018 | Seattle Sounders 2 | - | Sacramento Republic | 1:2 | ||||
| 4. Round | 03/06/2018 | Fresno FC | - | Seattle Sounders 2 | 4:0 | ||||
| 4. Round | 10/06/2018 | Seattle Sounders 2 | - | OKC Energy FC | 2:1 | ||||
| 5. Round | 06/07/2018 | Seattle Sounders 2 | - | Swope Park Rangers | 0:2 | ||||
| 5. Round | 08/07/2018 | Seattle Sounders 2 | - | Reno 1868 FC | 1:2 |  |
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| 5. Round | 15/07/2018 | Real Monarchs SLC | - | Seattle Sounders 2 | 2:0 | ||||
| 6. Round | 20/08/2018 | Portland Timbers 2 | - | Seattle Sounders 2 | 4:1 | |
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| 6. Round | 30/08/2018 | Seattle Sounders 2 | - | Saint Louis FC | 1:1 | ||||
| 7. Round | 02/09/2018 | Seattle Sounders 2 | - | Orange County SC | 1:1 | ||||
| 7. Round | 16/09/2018 | Seattle Sounders 2 | - | Phoenix Rising | 0:1 | ||||
| 8. Round | 04/10/2018 | Seattle Sounders 2 | - | Los Angeles Galaxy II | 2:2 | ||||
| 8. Round | 11/10/2018 | Seattle Sounders 2 | - | Colorado Springs Switchbacks | 2:2 | ||||
| 8. Round | 14/10/2018 | Tulsa Roughnecks | - | Seattle Sounders 2 | 1:4 |
USA