A cross-sectional study was carried out to determine iodine status of pregnant and lactating women in Arusha Municipality. Urine and salt samples were collected from a total of 429 respondents who were visiting Themi and Ngarenaro Reproductive and Child Care clinics. A structured questionnaire was used to collect socio-economic and demographic information from respondents and also wholesale and retail salt traders to ascertain their knowledge about iodised salt and IDD. Results revealed that, overall median UIC for pregnant women (33%) was 205 μg/l (95% CI; 26.7%, 39.2%), and lactating women (22.8%) was 155.5 μg/l (95% CI; 17.1%, 28.4%). Median UIC for pregnant women (62.9%) in Themi was 122 μg/l (95% CI; 46.6%, 79%), while median UIC for lactating women (28.2%) was 178.1 μg/l (95% CI; 20.8%, 35.5%). The median UIC for pregnant women (36.5%) at Ngarenaro was 233.9 μg/l (95% CI; 29.5%, 43.4%), while median UIC for lactating women (39.2%) was 123.5μg/l (95% CI; 27.6%, 50.7%). The recommended UIC for pregnant and lactating women range of 150-249 μg/l indicate adequate iodine intake. These results suggested that, those pregnant women from Themi ward had mild iodine deficiency while the lactating women had optimal iodine intake. Pregnant women from Ngarenaro ward had adequate iodine intake while for lactating women had mild iodine deficiency. About 34% (95% CI; 23%, 44%) of pregnant women had UIC above recommended safety levels of >500 μg/l which suggested that, pregnant women might have excessive iodine intake. Likewise, 15% (95% CI; 3%, 33%) of lactating women had UIC levels above the recommended levels of >500 μg/l suggesting that, lactating women could also be taking excessive iodine. Excessive intake iodine could be due to increased iodine intake from foods due to high levels ofiodine in salt used in cooking. It was concluded from the study that, most respondents had adequate iodine intake. However, 34% and 15% of pregnant and lactating women, respectively, had excessive iodine intake. There is a need to re- examine iodation levels to comply with the WHO recommended levels of 40 ppm at factory. Further studies involving large population groups should be done to ascertain the looming risk of iodine toxicity among pregnant and lactating women.