Mercury is the only metal that remains in liquid form at the room temperature. It is a very toxic metal and even short-term exposure can lead to poisoning. Mercury intoxication can affect many systems such as skin, cardiovascular, genitourinary, central and peripheral nervous, respiratory, and musculoskeletal system. Consequently, the diagnosis of mercury intoxication can be challenging due to its non-specific and multisystemic presentation. Herein, we report five pediatric cases with mercury intoxication from two families that were initially misdiagnosed as rheumatic disorders. We also performed a literature review about pediatric cases with mercury intoxication to investigate the clinical findings in children, the source of intoxication, and the current treatment preferences. As in our cases, reported patients were previously misdiagnosed as various infectious and/or rheumatic diseases before the diagnosis of mercury intoxication was established. A delay in diagnosis and treatment can cause serious morbidities and even mortality. We report this case series to emphasize the multisystemic presentation of mercury intoxication, and to remind and provide clues for physicians to recognize this rare toxicologic syndrome.