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 made online by the Ministry of Education.
They are either mixed or single-sex.
Here is a list of County Schools in Nyandarua County:
| NAME | KNEC CODE | TYPE | CATEGORY | |
| 1 | SHAMATA GIRLS SECONDARY SCHOOL | 07201103 | Girls | County |
| 2 | NGAINDEITHIA SECONDARY SCHOOL | 07201105 | Mixed | County |
| 3 | MUKOE SECONDARY SCHOOL | 07201106 | Mixed | County |
| 4 | KAHUHO SECONDARY SCHOOL | 07201115 | Mixed | County |
| 5 | MWENDA-ANDU SECONDARY SCHOOL | 07209103 | Mixed | County |
| 6 | KIMURI SECONDARY SCHOOL | 07209104 | Mixed | County |
| 7 | MKUNGI SECONDARY SCHOOL | 07209106 | Mixed | County |
| 8 | MURUAKI SECONDARY SCHOOL | 07209107 | Boys | County |
| 9 | SALIENT HIGH SCHOOL | 07213103 | Mixed | County |
| 10 | KALOU SECONDARY SCHOOL | 07213104 | Mixed | County |
| 11 | KABATI SECONDARY SCHOOL | 07214130 | Mixed | County |
| 12 | MIHARATI SECONDARY SCHOOL | 07215201 | Boys | County |
| 13 | NDEMI SECONDARY SCHOOL | 07215207 | Mixed | County |
| 14 | MIKEU SECONDARY SCHOOL | 07215217 | Mixed | County |
| 15 | KIPIPIRI SCHOOL | 07215223 | Boys | County |
| 16 | BONGO GIRLS SECONDARY SCHOOL | 07216102 | Girls | County |
| 17 | HENI SECONDARY SCHOOL | 07216110 | Mixed | County |
