| 2018 NYSAIS Class C Playoff Bracket | ||||
| PLAY-IN | QUARTERFINAL | SEMI FINAL | FINAL | |
| February 21, 2018 | February 22, 2018 | February 24, 2018 | February 26, 2018 | |
| 1 Knox (23-2) | ||||
| 76-57 | 1 Knox (24-2) | |||
| 9 Brooklyn Friends (17-6) | @ Highest Seed | |||
| 62-29 | 8 Loyola (15-6) | |||
| @ Sacred Heart | ||||
| 8 Loyola (14-6) | ||||
| 98-61 | 1 Knox (25-2) | |||
| @ Highest Seed | ||||
| 5 Staten Island Academy (20-6) | ||||
| 62-50 | 5 Staten Island Academy (21-6) | |||
| @ SI Academy | ||||
| 4 Martin Luther (14-6) | ||||
| 74-71 | 2 Masters (18-7) | |||
| @ Holy Child | Class C Champion | |||
| 3 Rye Country Day (12-11) | ||||
| 57-54 | 6 Berkeley Carroll (17-8) | |||
| @ Highest Seed | ||||
| 6 Berkeley Carroll (16-8) | ||||
| 68-55 | 2 Masters (17-7) | |||
| @ Highest Seed | ||||
| 7 Portledge (11-12) | ||||
| 73-48 | 2 Masters (16-7) | |||
| @ Highest Seed | ||||
| 2 Masters (15-7) | ||||