Autoimmune thyroiditis (AIT) is the most common autoimmune endocrine disorder, and recognizing infectious triggers like Yersinia enterocolitica is crucial for clinicians to improve diagnosis and management. A 53-year-old man presented with fatigue, irritability, sweating, and palpitations. Laboratory tests showed suppressed TSH, elevated FT3, normal FT4, and anti-TPO >1000 IU/mL. Western blot confirmed Yersinia enterocolitica infection through IgA and IgG detection, highlighting the importance of specific serological methods for accurate diagnosis. Mild lymphocytosis with relative neutropenia suggested immune activation. The diagnosis was autoimmune thyroiditis (AIT) with transient thyrotoxicosis triggered by Yersinia enterocolitica. Treatment with thiamazole and doxycycline resulted in complete resolution of symptoms and normalization of thyroid hormone levels. This case supports the hypothesis that Yersinia enterocolitica may trigger autoimmune thyroiditis through molecular mimicry and immune dysregulation, which can also affect male reproductive health, underscoring the importance of a comprehensive assessment. Screening for infectious cofactors, such as Yersinia enterocolitica, in men with thyroid autoimmunity is vital for accurate diagnosis and effective management, thereby encouraging clinicians to adopt proactive testing strategies.