Mucocele is clinical term used to describe swelling caused by the pooling of saliva at the site of a severed or obstructed minor salivary gland duct. Mucoceles are categorized into two subgroups, extravasation type and retention cyst type. The etiology of extravasation type mucocele is related to mechanical trauma to the minor salivary gland excretory duct, resulting in extravasation of mucus into the fibrous connective tissue so that a cyst-like cavity is produced, but the epithelial lining is absent. Retention cyst type mucocele results from obstruction of minor salivary gland excretory duct, and cystic cavity is lined by epithelial cells. This case report presents a mucocele occurred on the lower lip, and caused by suture silk unremoved for 3 years. Suture silk penetrated and tore the minor salivary gland duct on the lower lip with subsequent extravasation of mucus into the fibrous connective tissue.