ABSTRACT Background: The human body is composed of two types of elements, abundant and trace elements. Abundant elements include the major elements that are important constituents of tissues e.g. oxygen, carbon, nitrogen, and hydrogen. Trace elements are micronutrients which are important for the human body, but they are only present in traceable quantities. They are classified into essential, and non-essential elements. Essential trace elements include iron, zinc, copper, cobalt, fluoride, iodide, manganese, molybdenum & selenium. Probably essential trace elements include Nickel, tin, vanadium, silicon, Boron. Non-essential trace elements include aluminum, lead, silver, mercury, rubidium, strontium, titanium, and zirconium. Although trace elements account for only 0.02% of the total body weight, yet they have many functions in the biological process. Some of them like iron, zinc, chromium, copper and iodine act as antioxidants and cofactors for many enzymes affecting the metabolism and insulin action and have great effect on insulin and leptin receptors. Nevertheless, the biochemical functions are well-defined.  If the level of these micronutrients decreased or increased, widespread issues in human health occur. Aim: Some of the trace elements and their role in the pathology and development of obesity and diabetes mellitus are the subject of this article. Conclusion: This review concludes that deficiency or excess of some trace elements may contribute directly or indirectly to pathogenesis of diabetes mellitus and obesity. Further investigations are needed to complete gaps in our knowledge on trace elements.