Objective: This study is aiming at assessing the quality of external quality assessment control results of standard Immunological and Immuno-haematological control samples generated by clinical laboratories in Kiambu County. Design: This is a multi-site descriptive cross-sectional study. A total of 25 laboratories participated from all level in the external Quality Assurance program to determine the accuracy of the diagnostic results generated. Results: The findings are that the immune-haematological test results are reliable, with the overall Intra-class correlation coefficient (ICC) being 0.994. Four out of seven immunological results shows no variation from the control results. For those with variations, Cronbach’s alpha is 0.515, the interclass correlation was 0.245, and the level of significance is 0.01; therefore, the four results are unreliable and are examined individually to ascertain the cause of variation Conclusion: The diagnostic immune-haematological control results generated by different laboratories in Kiambu County have excellent reliability, meaning that the aspect of good laboratory practice towards quality is good. Some immunological results show variation; however, most are highly specific and sensitive. Recommendations: The government and stakeholders establish more working continuous external quality assessment programs. Further studies to be done on tests with significant variation to establish if it is the test kits or just misdiagnosis.