A cutaneous and soft tissue reaction that resulted from a broken thermometer inside the mouth of a 10-year-old boy is described. Metallic mercury globules and glass pieces were identified in the excised tissue. On histologic examination, a zone of necrosis, polymorphonuclear leukocytes, macrophages, and multinucleated giant cells surrounded metallic mercury that appeared as dark opaque globules. Dense fibrosis and reactive lymphoid hyperplasia were also noted in the dermis and deeper tissues. The gold lysis test, scanning electron microscopy, and energy-dispersive x-ray analysis confirmed the presence of mercury in the tissue. A literature review on cutaneous mercury granuloma illustrates its unpredictable course. The cutaneous reaction may remain localized, but some cases are associated with an elevated mercury level in blood and urine, pulmonary embolism, mercury poisoning, and even with fatal outcome. Various manifestations of mercury poisoning and guidelines for the management of cutaneous mercury granuloma are discussed.