Contamination of livestock feed with aflatoxin B1 (AFB1) results in the ingestion of this toxin by dairy animals, leading to its hydroxylation in the liver. The toxin is then converted into aflatoxin M1 (AFM1), which is subsequently excreted in milk. The presence of AFM1 in milk and dairy products represents a significant global public health concern. In this study, an analysis was conducted of the concentration of AFM1 in traditional milk (both raw and boiled) and yoghurt in Fasa, Fars Province. A total of 90 samples, including 30 samples from each of three distinct types of raw milk, boiled milk, and yoghurt, were collected during two seasons of summer and winter and then analyzed using enzyme-linked immunosorbent assay (ELISA). The findings indicated that the mean concentration of AFM1 in raw milk, boiled milk, and yoghurt was 297.05, 275.87, and 208.09 nanograms per liter (ng/L), respectively. The AFM1 concentration levels in all samples were found to exceed the permissible limits stipulated by both the Iranian national standard and the European Union (EU), while being lower than the limits set by the U.S. Food and Drug Administration (FDA). Moreover, the results indicated that AFM1 concentrations were elevated in milk samples during the winter months, while higher concentrations were observed in yoghurt during the summer. It is imperative to investigate the factors that affect AFM1 formation and to attempt to reduce it, given the detrimental effects of AFM1 on the health of individuals who consume milk and dairy products. The consequences of exposure to AFM1 have been found to be irreversible. In view of the findings, it is crucial to implement rigorous monitoring and control measures for animal feed with a view to reducing the risk of aflatoxin contamination.