The emergence of a religious movement and adoption of it by a society is inexplicably complex for a single reason. In this study, the reasons for the rapid spread of Mazdakism, emerged during the Sassanid period, were examined. The fact that the social classification was very strong at the time of its emergence and the public was uncomfortable with the practices of administrators and mowbads are among the reasons for the spread of this movement. In addition, wars and defeats, prolonged drought caused to spread the movement in a short time. Mazdak, who was also a mowbad, started a movement that would last its influence for centuries with a new religious interpretation he had put forward. In the period Mazdakism emerged, the events revealed by the Mazdakists overshadowed the religious interpretations which Mazdak had put forward. The study consists of an introduction and two parts. In the introduction, information was given about Mazdek and his teaching. In the first part, the social and economic characteristics of the Sassanid period were discussed. In the second part, the reasons for the emergence and spread of the Mazdek movement were examined.