Gestational diabetes Mellitus (GDM) is a disorder at pregnancy causing insulin intolerance thus contributing to adverse pregnancy outcomes. The aim of this study was to evaluate neonatal outcomes associated with gestational diabetes mellitus among pregnant women with GDM in Kisumu County, Kenya. A case-control study was carried out among 210 pregnant women in Kisumu County. Screening and diagnosis were performed using the 2013 WHO criteria. Data was collected using a checklist, mother-baby booklet and gynaecological files. Descriptive and inferential statistical analysis were done in SPSS V.23 using Chi-square (χ2) test to test for associations. Analysis revealed that of the 105 GDM cases, majority were in 30-34 years age group, married and employed. Further analysis revealed that neonatal macrosomia and neonatal admission to intensive care unit (all p<0.001) were significantly associated with GDM. Therefore, these findings suggests that due to these adverse neonatal outcomes, there is need for interventions such as early GDM screening and management among the women at high-risk group.