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 Machakos County:
| NAME | KNEC CODE | TYPE | CATEGORY | |
| 1 | KATOLONI SECONDARY SCHOOL | 12301707 | Mixed | County |
| 2 | KYANGULI MEMORIAL SECONDARY SCHOOL | 12301711 | Mixed | County |
| 3 | MUVUTI SECONDARY SCHOOL | 12301713 | Boys | County |
| 4 | KWANTHANZE AIC SECONDARY SCHOOL | 12301718 | Mixed | County |
| 5 | MIKUINI SECONDARY SCHOOL | 12301719 | Mixed | County |
| 6 | MUINDI MBINGU SECONDARY SCHOOL | 12301722 | Boys | County |
| 7 | ABC IVETI HILLS SECONDARY SCHOOL | 12301724 | Mixed | County |
| 8 | KATELEMBO CENTRE OF EXECELLENCE BOYS HIGH | 12301795 | Boys | County |
| 9 | MIU BOYS SECONDARY SCHOOL | 12314102 | Boys | County |
| 10 | KYETHIVO GIRLS’ SECONDARY SCHOOL | 12314105 | Girls | County |
| 11 | MAKUTANO SECONDARY SCHOOL | 12314108 | Mixed | County |
| 12 | IKALAASA SECONDARY SCHOOL | 12314109 | Mixed | County |
| 13 | KIBAUNI SECONDARY SCHOOL | 12314111 | Mixed | County |
| 14 | KIUNDWANI SECONDARY SCHOOL | 12314112 | Mixed | County |
| 15 | MBAIKINI BOYS HIGH SCHOOL | 12314202 | Boys | County |
| 16 | MWALA SCHOOL | 12314204 | Boys | County |
| 17 | LEMA GIRLS’ SECONDARY SCHOOL | 12314205 | Girls | County |
| 18 | ST. TERESA MWALA GIRLS’ HIGH SCHOOL | 12314206 | Girls | County |
| 19 | A.I.C. KUNIKILA SECONDARY SCHOOL | 12314208 | Mixed | County |
| 20 | BISHOP NDINGI HIGH SCHOOL | 12314210 | Mixed | County |
| 21 | MULU SECONDARY SCHOOL | 12314212 | Mixed | County |
| 22 | MAKIVENZI SECONDARY SCHOOL | 12315501 | Girls | County |
| 23 | NDALANI SECONDARY SCHOOL | 12315504 | Mixed | County |
| 24 | MATUU HGM MEMORIAL GIRLS HIGH SCHOOL | 12315505 | Girls | County |
| 25 | MAVOLONI SECONDARY SCHOOL | 12315506 | Mixed | County |
| 26 | KITHIMANI HGM SECONDARY SCHOOL | 12315507 | Mixed | County |
| 27 | KIVANDINI SECONDARY SCHOOL | 12315512 | Mixed | County |
| 28 | KATANGI SECONDARY SCHOOL | 12315601 | Boys | County |
| 29 | IKOMBE SECONDARY SCHOOL | 12315605 | Mixed | County |
| 30 | FR. MAKEWA HIGH SCHOOL | 12315608 | Mixed | County |
| 31 | NGUMBULU SECONDARY SCHOOL | 12315610 | Mixed | County |
| 32 | BISHOP PAUL MUTUA HIGH SCHOOL | 12315612 | Mixed | County |
| 33 | GOOD HOPE HIGH SCHOOL – KILAATU | 12315618 | Mixed | County |
| 34 | MANYATTA SECONDARY SCHOOL | 12316103 | Mixed | County |
| 35 | KAWETHEI S.A GIRLS SECONDARY SCHOOL | 12316105 | Girls | County |
| 36 | ST. MARTIN’S KITWII SECONDARY SCHOOL | 12316106 | Mixed | County |
| 37 | KYENI HIGH SCHOOL MIXED DAY & BOARDING | 12316119 | Mixed | County |
| 38 | MUISUNI GIRLS SECONDARY SCHOOL | 12316127 | Girls | County |
| 39 | MITABONI ABC GIRLS SECONDARY SCHOOL | 12329101 | Girls | County |
| 40 | MITABONI HIGH SCHOOL | 12329102 | Boys | County |
| 41 | KALILUNI GIRLS’ SECONDARY SCHOOL | 12329104 | Girls | County |
| 42 | LUKENYA GIRLS CENTRE OF EXCELLENCE | 12330135 | Girls | County |
| 43 | KIVAA SECONDARY SCHOOL | 12343303 | Mixed | County |
| 44 | KITHYOKO SECONDARY SCHOOL | 12343315 | Mixed | County |
| 45 | KINYUI BOYS SECONDARY SCHOOL | 12345502 | Boys | County |
| 46 | KINYUI GIRLS SA SECONDARY SCHOOL | 12345505 | Girls | County |
| 47 | KATWANYAA SECONDARY SCHOOL | 12345507 | Mixed | County |
| 48 | FR. HEERAN SECONDARY SCHOOL | 12345509 | Girls | County |
| 49 | KISUKIONI SECONDARY SCHOOL | 12345514 | Mixed | County |
| 50 | MUUMANDU SECONDARY SCHOOL | 12363101 | Mixed | County |
| 51 | KONZA ABC SECONDARY SCHOOL | 12363105 | Mixed | County |
| 52 | KIMUTWA SECONDARY SCHOOL | 12363107 | Mixed | County |
| 53 | AIC MBEMBANI CENTRAL SECONDARY SCHOOL | 12363110 | Mixed | County |
| 54 | MBUANI SECONDARY SCHOOL | 12363205 | Mixed | County |
| 55 | KIUU SECONDARY SCHOOL | 12363209 | Mixed | County |
| 56 | KALAMA SECONDARY SCHOOL | 12363304 | Mixed | County |
| 57 | KYANGALA SECONDARY SCHOOL | 12363305 | Boys | County |
| 58 | KYANGALA GIRL’S SECONDARY SCHOOL | 12363306 | Girls | County |
| 59 | MBUKUNI SECONDARY SCHOOL | 12363309 | Mixed | County |
| 60 | MANG’AUNI SECONDARY SCHOOL | 12363311 | Mixed | County |
