Hemophagocytic lymphohistiocytosis (HLH) is an aggressive hematologic disease based on widespread immune activation and tissue destruction. This uncommon condition can be primary as well as secondary to infection or malignancy. However, HLH diagnosis rarely contributes to unveiling an underlying malignancy. The most crucial prognostic factor of HLH is timely diagnosis and treatment. However, due to the rarity of this syndrome and the variable clinical presentations, HLH is often underdiagnosed. A 12-year-old boy complained of recurrent fever and fatigue for the past four months. He presented with pancytopenia, hyperferritinemia, hypertriglyceridemia, elevated liver enzymes, and a severe inflammatory profile. The diagnosis of HLH disease was established. During further evaluation, a right subaxillary palpable lymph node was found. The biopsy revealed a peripheral T-cell lymphoma, not otherwise specified (PTCL, NOS). The bone marrow was also infiltrated with evidence of dissemination to the skeleton on a positron emission tomography (PET) scan (stage IV). The patient was treated with six cycles of CHOEP (cyclophosphamide, doxorubicin, oncovin, etoposide, prednisone) protocol but relapsed and passed away three months later. This case report sheds light on the importance of early recognition and treatment of HLH, as well as searching for underlying malignancy or disease, even in young patients.