Introduction: Non-alcoholic fatty liver disease is often an asymptomatic condition one of the leading causes of chronic liver disease and is associated with an increase in cardiovascular morbidity. Being overweight or obese has been positively linked to non-alcoholic fatty liver disease in children. There is evidence to show that when detected early, non-alcoholic fatty liver disease is reversible primarily upon institution of lifestyle changes targeted at weight reduction. Establishing the prevalence of non-alcoholic fatty liver disease in overweight and obese Kenyan children would serve as a benchmark for long term monitoring of associated morbidity and guide in public health policies aimed at early screening and intervention. Objectives: The aim of this study was to investigate prevalence of non-alcoholic fatty liver disease in overweight and obese children aged between six and eighteen years using liver ultrasonography. Methodology: A descriptive cross sectional study was carried out in 103 overweight and obese school aged children aged six to eighteen years seeking ambulatory health care services in Nairobi. Consent was obtained from the primary caregivers. A questionnaire was administered to collect information on bio data. Blood pressure readings were taken and plotted in age and gender specific charts and a liver ultrasound was done to assess and grade fatty changes. Data Analysis: Statistical analyses were conducted using SPSS version 11.5 (SPSS, Chicago, IL, USA). Categorical variables were analyzed using median (IQR) and summarized using frequency counts and percentages. Chi-square test was used to determine odds ratios for association between presence of fatty liver and other categorical variables using 2x2 tables. All clinically important variables were then included in multiple logistic regression model adjusting for age and sex to find if there was any association with fatty liver. All analyses were two-tailed and P-value less than 0.05 was considered statistically significant. Results: A total of 103 children were recruited in the study. The prevalence of fatty liver change was 26.2% (27/103; 95%CI=18.0%-35.8 %). There was no association between sex and fatty liver disease (OR=1.13, p=0.82; 95%CI=0.4-3.2) Obese children were four times more likely to have fatty liver compared to overweight children (OR=4.52 p=0.02, 95%CI=1.4-19.0). Slightly more than a third of the children, 40.8% (n=41) had elevated blood pressure. However, there was no association between elevated blood pressure and fatty liver disease (OR=2.06; p=0.27; 95%CI=0.6-7.6). Older children (13-18 years) were four times more likely to have fatty liver vi