Abstract Background & Objectives: Yoghurt is a fermented dairy produced by starter culture and consumed around the world. This food may become contaminated with aflatoxin M1 that caused threats to the health of consumers, especially young children and adults. So detoxification with biological methods is the best solution in milk and fermented dairy products. The aim of this study was to evaluate the effect of starter bacteria and lactobacillus casei in the reduction of aflatoxin M1 in Yoghurt. Materials & Methods: Milk contaminated artificially with aflatoxin M1 (AFM1) at levels of 0.05, 0.1, 0.5, and 0.75 (ppb). Then starter was added and incubated at 42°C. In next step the cold yoghurt was centrifuged and the amount of aflatoxin M1 residue in the supernatant was measured by ELISA method. Finally, the results were analyzed with the SPSS 16. Results: The analysis of yoghurts during manufacturing with starter YC-280, L.casei-431 showed that the mean percentages of absorbance were 94.35% and 94.15% respectively. Conclusion: Starter culture of yoghurt and probiotic strain L.casei-431 are safe methods that can be used for detoxification without losing nutritional value