In Kenya, 1 in every 5 adolescents is either a mother or already pregnant. Teen mother face different challenges, one main challenge being lack of maternal skills. The study examined the Environmental risk factors and management practices of diarrheal disease among adolescent mothers in Kisumu County, Kenya. The study employed a cross-sectional study using mixed methods approach for data collection. The study targeted 454 adolescent mothers from which 294 adolescent mothers aged 15-19 years were determined using Cochrane’s formula. Data was collected using questionnaires and focus group discussion and analysed using STATA version 16 and NVIVO version 12. Descriptive statistics were presented using frequency tables and figures. Binary logistic regression was done to determine the association between the independent and dependent variables (AOR, 95%CI; p<0.05). Diarrhoea prevalence here was higher (22.5%) than the national one (15%) and that 34% of the adolescent mothers had poor diarrhoea management practices. Further, number of children under-five in a household, bottle- feeding, and vaccination status were predictors of diarrhoea. Having a handwashing facility within the household also influenced the diarrhoea management practices. The study recommended that adolescent mothers should be sensitized about proper feeding practices, importance of vaccination and supporting sanitation and hygiene in the household level to reduce diarrhoea prevalence child under five. Thus, the results would be utilized to set interventions that support the adolescent mother with more information on proper diarrhoea management practices.