We describe the clinical presentation, diagnosis, treatment, and follow-up data of a 39-year-old woman with asymptomatic right kidney tumor, which was later histopathologically diagnosed as metanephric adenoma (MA). Macroscopically, the tumor had integrity tegument with homogeneous and gray cutting surface. Microscopically, the tumor cells were formed in adenoid or papillary pattern and contained psammoma bodies, without distinctive atypia. Immunohistochemistry results showed they were negative for creatine kinase 7, epithelial membrane antigen, and renal cell carcinoma, and positive for AE1/AE3, vimentin, and Wilms Tumor 1. Pathological diagnosis was MA. The 48 months' follow-up information was available without recurrence.According to this case and literature review, we figured that it is difficult to make a definite diagnosis of MA only by image examination. Nephron-sparing surgery is eligible to treat MA. Long-term active surveillance is necessary because of the uncertainty of the biological behavior and cellular origin of MA.