Objective: This study aims to determine the diagnostic utility of the International Academy of Cytology (IAC) Yokohama System for reporting breast cytopathology in lesions of the male breast. Study Design: Fine-needle aspiration biopsy (FNAB) reports between 2015 and 2019 were retrospectively recategorized according to the 5-tiered IAC Yokohama Reporting System. Our database yielded a total of 1,532 FNAB reports from breast lesions, obtained from 1,350 male patients. The risk of malignancy (ROM) and diagnostic performance of FNAB were determined using follow-up histopathological diagnosis and/or clinical follow-up, where available, for each category. Results: The category distribution were as follows: inadequate, 40%; benign, 57%; atypical, 0.6%; suspicious for malignancy, 0.7%; and malignant, 1.6%. The ROM in each category was nondiagnostic, 11%; benign, 3%; atypical, 28%; suspicious for malignancy, 56%; and malignant, 100%. The sensitivity, specificity, positive predictive value, and negative predictive value were recorded as 63, 100, 100, and 84.6% respectively, when only malignant cases were considered as positive tests. Conclusion: This study validates the IAC Yokohama System for reporting male breast cytopathology. In accordance with the aim of the Yokohama System to establish best practice guidelines for reporting breast cytopathology, this comprehensive scheme facilitates comparisons between local and international institutions. The ROM acts as an internal audit for quality assurance within one’s own laboratory and provides guidance for clinical management. It highlights inefficiencies such as high inadequacy rates for category 1 and also features strengths with impressive specificity for categories 4 and 5.