Children are particularly vulnerable to chemical pollution arising from heavy metals and metalloids; these environmental toxicants can result in disease and disability that will remain throughout the lifespan. The urinary elemental excretion of metals and metalloids was measured in children, aged between six and 15 years, living in the textile, tannery, and multiple industries dominated areas of Dhaka, Bangladesh; these were compared with results from a reference control area. The accurate measurement of urinary concentrations of twenty-two metals and metalloids was accomplished using a simple and robust ICP-MS method; hydration variations were adjusted by osmolality. Results revealed that children living in the textile, tannery, and multiple industry areas were exposed to a greater extent to the environmental pollutants arsenic, chromium, iron, selenium, molybdenum, tin, caesium, thallium, and lead when compared to control children, after adjusting for confounding factors such as age, sex, and nutritional status. The observation of a significantly increased urinary excretion of manganese (Mn) and higher concentrations of Mn in the drinking water of the textile area (131.0 µg/L, p < 0.05) suggest that children living in that area may be at an elevated risk of attention-deficit/hyperactivity disorder; about 70% of drinking water samples exceeded the national recommended limit of 100 µg/L. In addition, chromium exposure was measured at the highest levels in children living in the tannery area while children living in the multiple industry area were exposed to high levels of arsenic, cadmium, and lead which imply a high risk of metals-induced renal and neurological damages to exposed children. This study reveals the issue of metals and metalloid pollution in children in the industrialised areas of Bangladesh and demonstrates the increased risk of health problems. These findings reinforce the need to regulate and control potential sources of metal and metalloid pollution.