Our aim was to evaluate the clinical value of splenectomy as a treatment for relapsed hemophagocytic lymphohistiocytosis (HLH) of unknown cause in adults. We retrospectively reviewed the clinical data from medical records of 19 adults with relapsed HLH of unknown cause treated with splenectomy in our institution from June 2007 to March 2014. To rule out possible underlying diseases, including infection, autoimmune disease, neoplasms, and primary HLH, the patients had undergone examinations including F18 fluoro-2-deoxyglucose positron emission tomography/computed tomography, HLH-associated gene defects, and lymph node biopsies. Twelve patients (63.2 %) achieved partial responses (PR), whereas seven patients (36.8 %) had no response (NR) prior to splenectomy. Infection and hemorrhage were the main complications of splenectomy. Eighteen cases were evaluable after follow-up. Seven cases with histopathologic diagnoses of lymphoma had received chemotherapy, four of whom had achieved complete responses (CR), one PR, and two NR. Maintenance treatment was ceased 2 or 3 months after splenectomy in the other 11 cases, five of whom had CR, four PR, and two NR. Eleven of 18 cases (61.1 %) survived with a median follow-up of 25 months (range 3-79 months) for survivors. Twelve- and 36-month progression-free survival rates were 48 and 24 %, respectively; 12- and 36-month overall survival rates were 57 and 25 %, respectively. Median survival time was 22 months. Our results indicate splenectomy may be an effective means of diagnosis and treatment of relapsed HLH of unknown cause. Further study is required to establish the mechanism and value of splenectomy in this disease.