Peripheral T-cell lymphomas (TCLs) are a heterogeneous group of aggressive, uncommon forms of T-cell or natural killer cell-derived non-Hodgkin's lymphomas. Acute tumor lysis syndrome (TLS) is a multiple metabolic derangement that occurs due to the treatment of malignancies or spontaneous tumor cell death. We report the case of a 56-year-old male patient who presented with marked eosinophilic leukocytosis, rash, and lymphadenopathy at the initial visit but finally manifested with TCL and spontaneous TLS. On the first visit, hemogram showed a marked eosinophilic leukocytosis and raised lactate dehydrogenase. The patient refused for admission; however, lymph node biopsy was done on day-care basis. After 3 days, the patient presented in the emergency room with shortness of breath, altered renal and liver parameters, and dyselectrolytemia. Based on histopathological with immunohistochemistry findings on lymph node biopsy and clinical and laboratory finding, the patient was diagnosed as TCL-not otherwise specified with TLS.