We report a case of reactive lymphoid hyperplasia (RLH) of the liver in a 72-year-old woman without any symptoms. To our knowledge, only 11 other cases of this disease have ever been reported. The lesion was found incidentally during a medical examination, as a hypoechoic mass in segment 3 of the liver on ultrasonography. The findings of computed tomography, magnetic resonance imaging, and angiography suggested a malignancy. Frozen section diagnosis of an intraoperative needle biopsy suggested malignant lymphoma, so we performed lateral segmentectomy of the liver. Macroscopically, the tumor was well defined, white, and firm. Microscopically, there was polymorphous lymphoplasmacytic infiltration, with various-sized and -shaped lymphoid follicles. Lymphocytic infiltration was also observed in the portal tracts around the nodular lesion. Immunohistochemical study revealed polyclonality, confirming a pathological diagnosis of RLH of the liver. We discuss the clinicopathologic characteristics of this unusual disease.