Background: The paper describes a diagnostically challenging case of recurrent fever with an atypical course in a 55-year-old man. The authors highlight the significant difficulty in reaching a correct diagnosis, as well as the doubts and problems associated with the diagnostics. They suggest considering brucellosis as a diagnosis based on the patient's history and the course of the disease characterized by fluctuating, intermittent, and nocturnal fever. Objective: The aim of the study was to present an atypical and diagnostically challenging case of recurrent febrile episodes in a 55-year-old man. Material and methods: A comprehensive diagnostic workup, including laboratory tests, imaging, and specialist consultations, was conducted. The patient's medical history, physical examination, and various diagnostic tests were analyzed. Results: In a patient with recurrent episodes of fever, an infection with Brucella spp. was detected, which was effectively treated with long-term antibiotic therapy. Imaging and laboratory diagnostics, along with specialist consultations, helped rule out other potential causes of the symptoms. The patient achieved lasting improvement following the treatment. Conclusions: There is a high probability that the patient was infected with Brucella bacteria. Diagnostic challenges and the rarity of the disease, considered non-existent in Poland, hinder prompt confirmation or exclusion of infection. The authors aimed to highlight the possibility of a higher frequency of brucellosis in Poland. They suggest that Brucella bacteria may still be present, causing chronic, unrecognized, recurrent fevers. Based on the case analysis, the authors indicate that the frequent occurrence of this disease in Poland might be higher than reported by statistics.