Background <p>Renal dysfunction is one of the complications of malignancy which can be due to malignancy itself, treatment related and or other associated medical complications, which is associated with increased mortality among under five children in low-income countries. Despite the high mortality reported, studies on renal dysfunction in children with malignancy on chemotherapy are limited in low and middle-income settings. Therefore, the current study aimed to determine the prevalence, predictors and short-term outcomes of renal dysfunction among children aged 1 to less than 18 years with malignancy on chemotherapy at two tertiary hospitals in Tanzania.</p> Methods <p>In this cross-sectional study with follow up component, a total of 142 children aged 1 to less than 18 years were enrolled during a 6 months’ time period at Muhimbili National Hospital and Benjamini Mkapa Hospital from December 2024 to May 2025. Socio-demographic, clinical and laboratory data were collected using a structured questionnaire. Estimated glomerular filtration rate was calculated using Revised Schwartz formula. Renal dysfunction was defined as urinary albumin-to-creatinine ratio &gt; 30&#xa0;mg/g and or Estimated Glomerular Filtration Rate of &lt; 60&#xa0;ml/min/1.73m2. Data analysis was done using SPSS version 27 and statistical significance was assumed for factors with p-value &lt; 0.05.</p> Results <p>Out of 142 children, the overall prevalence of renal dysfunction was found to be 29.58%. Children with hematological malignancies were 6 times likely to experience renal dysfunction compared to those with solid malignancies APR 6.377[1.899,21.419] <i>p</i> = 0.0027 Similarly, the likelihood of Renal Dysfunction based on time of chemotherapy exposure among those within initial days of chemotherapy were 3.9 likely compared to those above 30 days APR3.918[1.230,12.483]<i>p</i> = 0.0209. Other variables, including, stage of malignancy, the use of combination therapy such as surgery and radiotherapy, did not show statistically significant associations with renal dysfunction.</p> Conclusion <p>Renal dysfunction is common among children with malignancy on chemotherapy. It is associated with undetected and asymptomatic renal dysfunction with short-term complications. Further studies are needed to determine the burden of renal dysfunction among children with malignancy while on treatment as compared to those with malignancy prior to initiation of chemotherapy, focusing on timing of chemotherapy initiation for early prevention, detection and early treatment.</p>