Background: Infectious diarrhea remains a significant global health concern, especially in less developed regions. The disease's impact on children under five years old is particularly severe, causing a high mortality rates in Low- and Middle-income Countries (LMICs). Objectives: The study aimed to investigate to characterize bacterial causative agents of diarrhea among children below 5 years attending Kiandutu Health care center in Thika, Kiambu County. It also sought to determine the antibiotic susceptibility testing of the isolated bacteria among children below 5 years attending Kiandutu Health care center in Thika, Kiambu County. Materials and Methods: The study utilized an exploratory descriptive approach because it will look at the many aspects of the disease incidence, including the onset of disease and treatment for the children attending Kiandutu Health Centre. Results: In characterizing the bacterial causative agents of diarrhea, Escherichia coli was isolated in 45.1%. In the remaining cases, in 54.9%, there was no growth or no pathogen isolated. In addition, MDR, which was defined as resistance to at least one agent in three different antimicrobial categories, was highly prevalent; it was identified in 78.3% (36/46) of the isolates. By stratification according to their ESBL status, all the ESBL-positive isolates showed MDR at 100% (23/23), compared to 56.5% (13/23) among the ESBL-negative isolates. The most sensitive antibiotic was chloramphenicol: 40 isolates were found to be sensitive and 6 resistants, giving a 13% resistance rate. Second to this was Amoxyclav, with 37 sensitive and 8 resistant. moderately effective antibiotic was ciprofloxacin, with 28 sensitive, 13 resistant, and 5 intermediates, yielding a 28.3% resistance rate. Conclusions and Recommendations: Resistance is ubiquitous, even among infections acquired within communities. Empiric antibiotic treatment is increasingly ineffective, with most first-line drugs failing against common pathoge