County secondary schools in Kenya form the third tier after national and extra-county schools respectively.
Most of Kenyan learners are absorbed by these schools.
Admission to county schools is done online by the Ministry of Education.
They are either mixed or single-sex.
Here is a list of county schools found in Mandera County
| SCHOOL KNEC CODE | NAME | CATEGORY | TYPE | |
| 1 | 47803113 | NEBOI SECONDARY SCHOOL | County | Boys |
| 2 | 47803123 | AL-BUKHARI MIXED SECONDARY SCHOOL | County | Mixed |
| 3 | 47803202 | HARERI MIXED SECONDARY SCHOOL | County | Mixed |
| 4 | 47803204 | ARESA GIRLS SECONDARY SCHOOL | County | Girls |
| 5 | 47803301 | KHALALIO SECONDARY SCHOOL | County | Boys |
| 6 | 47803302 | KHALALIO GIRLS SECONDARY SCHOOL | County | Girls |
| 7 | 47810101 | TAKABA BOYS’ SECONDARY SCHOOL | County | Boys |
| 8 | 47810105 | DANDU SECONDARY SCHOOL | County | Boys |
| 9 | 47810106 | BURDURAS SECONDARY SCHOOL | County | Boys |
| 10 | 47811101 | ELWAK SECONDARY SCHOOL | County | Boys |
| 11 | 47811103 | ELWAK GIRLS SECONDARY SCHOOL | County | Girls |
| 12 | 47811301 | WARGADUD MIXED SECONDARY SCHOOL | County | Mixed |
| 13 | 47812102 | RHAMU GIRLS SECONDARY SCHOOL | County | Girls |
| 14 | 47812201 | ASHABITO SECONDARY SCHOOL | County | Boys |
| 15 | 47812202 | RHAMU DIMTU BOYS SECONDARY | County | Boys |
| 16 | 47812203 | ASHABITO GIRLS SECONDARY SCHOOL | County | Girls |
| 17 | 47814101 | LAFEY BOYS SECONDARY SCHOOL | County | Boys |
| 18 | 47814201 | GARI SECONDARY SCHOOL | County | Boys |
| 19 | 47817104 | MALKAMARI BOYS SECONDARY SCHOOL | County | Boys |
| 20 | 47822101 | CHIEF MOHAMED JARI SECONDARY SCHOOL | County | Boys |
| 21 | 47822103 | KUTULO GIRLS MODEL SECONDARY SCHOOL | County | Girls |
| 22 | 47824101 | ARABIA BOYS SECONDARY SCHOOL | County | Boys |
| 23 | 47824102 | ARABIA GIRLS SECONDARY SCHOOL | County | Girls |