| OFSAA 2023 Boys Basketball Participants |
| A | AA | AAAA |
| CISSA The York School | CISSA Crescent School | CISAA CISAA St Michael Catholic High School |
| COSSA Kenner Collegiate Vocational Institute | COSSA Crestwood Secondary School | COSSA St Peter Catholic Secondary School |
| COSSA Nicholson Catholic College | CWOSSA McKinnon Park Secondary School | CWOSSA Cameron Heights Collegiate Institute |
| CWOSSA Walkerton District Community School | EOSSAA Thousand Island Secondary School | EOSSAA Frontenac Secondary School |
| EOSSAA Almonte District High School | GBSSA St Joseph’s Catholic High School (Barrie) | GBSSA Bradford District High School |
| GBSSA Our Lady of the Bay Catholic High School | GHAC King’s Christian Collegiate | GHAC St. Jean de Brébeuf Catholic Secondary School |
| GHAC École secondaire catholique Sainte– Trinité | LOSSA Holy Trinity Catholic Secondary School | LOSSA Ajax High School |
| LOSSA Monsignor John Pereyma Catholic Secondary School | NCSSAA Ashbury College | NCSSAA Glebe Collegiate Institute |
| NCSSAA Notre Dame High School | NCSSAA All Saints Catholic High School | NOSSA La Salle Secondary School |
| NEOAA Timmins High and Vocational School | NEOAA École secondaire catholique Thériault | ROPSSAA St. Marcellinus Catholic Secondary School |
| NOSSSA White Plains Collegiate | NOSSA Lo-Ellen Park Secondary School | SOSSA Saltfleet District High School |
| NWOSSAA Northern Lakes School | NWOSSAA Westgate Collegiate Vocational Institute | SOSSA Eden High School |
| SOSSA Hamilton District Christian High School | ROPSSAA, Ascension of Our Lords Catholic Secondary School | SWOSSAA Holy Name Catholic High School |
| SOSSA École secondaire catholique Saint Jean de Brébeuf | SOSSA St Francis Catholic Secondary School | TDCAA Father Henry Carr Catholic Secondary School |
| SWOSSAA École secondaire catholique E J Lajeunesse | SOSSA Dundas Valley Secondary School | TDSSAA Oakwood Collegiate Institute |
| SWOSSAA Maranatha Christian Academy | SWOSSAA Kennedy Collegiate | TDSSAA Richview Collegiate Institute |
| TDCAA Crawford Adventist Academy | TDCAA St Mother Teresa Catholic Academy | WOSSAA A B Lucas Secondary School |
| TDSSAA Downsview Secondary School | TDSSAA Silverthorn Collegiate Institute | YRAA The Dr G W Williams Secondary School |
| WOSSAA Mitchell District High School | WOSSAA St Joseph’s Catholic High School (St Thomas) | |
| YRAA École secondaire catholique Renaissance | YRAA, Thornlea Secondary School | |
