In this research, the belief in Mahdism is considered among the young Tehrani people aged 15 to 29. The method for research is descriptive and measurement-based and the statistical community samples from all the young Tehrani people aged 15 to 29. The quantity of sample is 691 participants chosen randomly and purposely from the northern, southern, western and eastern parts of Tehran. The tool for measurement, the questionnaire, has five parts which considers 24 questions and 24 phrases. The reliability index of the questionnaire is calculated as 80 percent. For data analysis and interpretation, descriptive, frequency, and percentiles were applied using One-sample T-test. The conclusions have demonstrated that belief in Mahdi is 3.08, a little above average of 3, and waiting for the appearance is 3.42, as above the average of 3 from 4 scales. Most of the participants in groups answered 4 in terms of knowledge of the Revered Mahdi (the saviour). Most of the correct answers regarding the philosophy of his occultation were identified as: protecting him from early martyrdom, preservation of the faith and constancy in religiousness. Most of the correct answers for the philosophy of appearance were identified as the enlightenment of truth and decay of the falsehood, establishment of a single global government and implementation of God’s faith.