Adult testicular granulosa cell tumor is a rare, potentially malignant sex cord-stromal tumor, of which 30 cases have been described to date. We report the case of a 43-year-old male who complained of a left testicular swelling. Scrotal ultrasound showed a cystic lesion, suggestive of hydrocele. However, due to a clinical suspicion of a solid-cystic neoplasm, a high inguinal orchidectomy was performed, which, on pathological examination, was diagnosed as adult granulosa cell tumor. Adult testicular granulosa cell tumors have aggressive behaviour as compared to their ovarian counterparts. They may rarely be predominantly cystic and present as hydrocele. Lymph node and distant metastases have been reported in few cases. Role of MIB-1 labelling index in prognostication is not well defined. Therefore, their recognition and documentation of their behaviour is important from a diagnostic, prognostic and therapeutic point of view.