We present the case of a 67-year-old male patient admitted to our clinic due to weakness and repeated dizziness. Due to his severe microcytic anemia in his laboratory tests, he needed a transfusion of 6 units of selected blood in the days following admission. Our patient was diagnosed with beta-thalassemia minor, which was accompanied by a severe deficiency of vitamin B12. Surprisingly, parallel to vitamin B12 deficiency, we detected laboratory abnormalities indicating complement-mediated autoimmune hemolysis. After correcting the vitamin B12 deficiency, the patient’s blood count improved, and the observed immunological abnormalities disappeared. Genetic testing of the hemoglobin gene confirmed the c.118C>T (p.Gln40STOP) variant in heterozygous form. Beta-thalassemia is a relatively common hematological disease, although rarely encountered in Hungary. Genetic testing of patients is possible at the Laboratory Medicine Institute of the Clinical Center in Debrecen. Unfortunately, we do not have accurate information about published domestic epidemiological data. Furthermore, establishing a diagnosis can be difficult if the disease is combined with other hematological disorders, such as the lack of vitamin B12, which can clinically mimic hemolytic anemia in certain features. Our case is considered a rarity in the literature, so in the case of a positive family history, it is recommended to screen immediate family members, which may facilitate the accurate establishment of a later diagnosis. Orv Hetil. 2023; 164(24): 954-960.