A Dissertation Submitted in Partial Fulfillment of the Requirements for the Degree of Master’s in Life Sciences of the Nelson Mandela African Institution Sciences and TechnologyTanzania is one of the countries where excessive iodine intake has been reported; hence intervention and identification of possible causes is required. The present study assessed iodine status and determined the critical contributors to excessive iodine intake in school children from Kinondoni, Tanzania. A total of 322 pupils and 30 food vendors provided salt samples for iodine analysis. Urinary iodine concentration (UIC) was spectrophotometrically determined in 266 sub-sampled children using the ammonium-persulfate digestion method. Information on dietary habits was collected using the Food Frequency Questionnaire and 24 hours dietary recall. Anthropometric values were determined by measuring children’s height and weight. Moreover, Knowledge, Attitude, and Practices study was done using a modified specific iodine deficiency-related questionnaire. Of the salt samples, 87% were adequately iodized with mean 53.94 ± 13.02, indicating over iodization. The median UIC was 401 µg/L, signifying excessive iodine intake. Twelve percent were overweight or obese and only 46.6% of pupils and 53.3% of food vendors had good knowledge of iodized salt utilization. Discretionary salt use (67.3%), higher consumption of potato chips (53.5%) and fried cassava (59.0%) were associated with a higher risk of excessive iodine intake. Potato chips (Adjusted Odds Ratio [AOR] =9.04, 95% CI: 3.61-22.63) and fried cassava consumption for 4-7 days/week (AOR=11.08, 95% CI: 3.4535.54) were significantly associated with excessive iodine intake. Discretionary salt intake significantly contributes to the high iodine status of schoolchildren in the study area. This effect can be reduced by public health campaigns to decrease salt consumption and improve salt iodation practices.