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 secondary schools in Kiambu County:
| NAME | KNEC CODE | CATEGORY | TYPE | |
| 1 | RIABAI HIGH SCHOOL | 11205206 | County | Boys |
| 2 | THIKA GIRLS KARIBARIBI SECONDARY SCHOOL | 11207125 | County | Girls |
| 3 | NGENIA HIGH SCHOOL | 11211301 | County | Boys |
| 4 | NGARARIGA GIRLS SECONDARY SCHOOL | 11211303 | County | Girls |
| 5 | THIGIO BOYS SECONDARY SCHOOL | 11211305 | County | Boys |
| 6 | MIRITHU SECONDARY SCHOOL | 11211307 | County | Girls |
| 7 | ST. MARY’S GIRLS – THIGIO | 11211308 | County | Girls |
| 8 | KAMANDURA GIRLS HIGH SCHOOL | 11211313 | County | Girls |
| 9 | ITURU HIGH SCHOOL | 11212102 | County | Boys |
| 10 | MURURIA SECONDARY SCHOOL | 11212103 | County | Boys |
| 11 | KAHUGUINI SECONDARY SCHOOL | 11212104 | County | Mixed |
| 12 | GATITU SECONDARY SCHOOL | 11212105 | County | Girls |
| 13 | KARINGA GIRLS’ HIGH SCHOOL | 11212106 | County | Girls |
| 14 | KIMUNYU SECONDARY SCHOOL | 11212108 | County | Boys |
| 15 | ICACIRI SECONDARY SCHOOL | 11212109 | County | Mixed |
| 16 | KIBIRU SECONDARY SCHOOL | 11212110 | County | Girls |
| 17 | MUTHIGA GIRLS’ SECONDARY SCHOOL | 11212114 | County | Girls |
| 18 | GATHIRU SECONDARY SCHOOL | 11212115 | County | Mixed |
| 19 | UCEKEINI SECONDARY SCHOOL | 11212117 | County | Girls |
| 20 | QUEEN OF PEACE NEMBU SECONDARY SCHOOL | 11212118 | County | Mixed |
| 21 | MUTUNGURU SECONDARY SCHOOL | 11212121 | County | Mixed |
| 22 | GATHURI SECONDARY SCHOOL | 11212123 | County | Mixed |
| 23 | KIAMWORIA SECONDARY SCHOOL | 11212128 | County | Mixed |
| 24 | MOI GIRLS SECONDARY SCHOOL KAMANGU | 11230202 | County | Girls |
| 25 | KIKUYU BOYS HIGH SCHOOL | 11230315 | County | Boys |
| 26 | KIKUYU DAY SECONDARY SCHOOL | 11230401 | County | Boys |
| 27 | MUSA GITAU SECONDARY SCHOOL | 11230406 | County | Girls |
| 28 | GATAMAIYU BOYS HIGH SCHOOL | 11231101 | County | Boys |
| 29 | GACHOIRE SECONDARY SCHOOL | 11231104 | County | Girls |
| 30 | LARI BOYS SECONDARY SCHOOL | 11231201 | County | Boys |
| 31 | KAMBAA GIRL’S HIGH SCHOOL | 11231203 | County | Girls |
| 32 | KINALE GIRLS HIGH SCHOOL | 11231204 | County | Girls |
| 33 | KAMBUI GIRLS’ HIGH SCHOOL | 11232101 | County | Girls |
| 34 | GATHIRIMU GIRLS TECHNICAL HIGH SCHOOL | 11232104 | County | Girls |
| 35 | GITWE GIRLS SECONDARY SCHOOL | 11232107 | County | Girls |
| 36 | KOMOTHAI BOYS HIGH SCHOOL | 11232301 | County | Boys |
| 37 | GATHIRU-INI SECONDARY SCHOOL | 11232302 | County | Boys |
| 38 | J G KIEREINI SECONDARY SCHOOL | 11232303 | County | Boys |
| 39 | KOMOTHAI GIRL’S TECHNICAL SCHOOL | 11232304 | County | Girls |
| 40 | MUNYU GIRLS HIGH SCHOOL | 11233301 | County | Girls |
| 41 | NGOLIBA SECONDARY SCHOOL | 11233302 | County | Mixed |
| 42 | ST. PAUL’S GATUANYAGA SECONDARY SCHOOL | 11233303 | County | Boys |
| 43 | KAIRI SECONDARY SCHOOL | 11236102 | County | Boys |
| 44 | GAKOE HIGH SCHOOL | 11236105 | County | Girls |
| 45 | OUR LADY OF FATIMA KIRIKO GIRLS SECONDARY SCHOOL | 11236106 | County | Girls |
| 46 | GATUNGURU SECONDARY SCHOOL | 11236111 | County | Boys |
| 47 | GIKINDU SECONDARY SCHOOL | 11236116 | County | Girls |
| 48 | MAKWA SECONDARY SCHOOL | 11236119 | County | Boys |
| 49 | ST. ANGELAS GIRLS HIGH SCHOOL KARURA | 11240110 | County | Girls |
| 50 | KIRANGARI HIGH SCHOOL | 11241002 | County | Boys |
| 51 | KAHUHO UHURU HIGH SCHOOL | 11241012 | County | Boys |
| 52 | KANJERU GIRLS’ HIGH SHOOL | 11241014 | County | Girls |
| 53 | UTHIRU GIRLS HIGH SCHOOL | 11241015 | County | Girls |
