The main purpose of the present study is to find hidden meanings of sexual sin experiences and also to investigating how these meanings are constructed socially. The results of the phenomenological analysis of sexual  sin  experiences among 7 female participants (Iranian/ Shi’a) who had sexual relation with the opposite sex (out of religious/ legal marriage) indicated that  sexual sin experience starts from a simple chat and acquaintance with the opposite sex and in a short time leads to courtship and sexual relations. Secondly, before committing the sin and in the first sexual sin experience, the perpetrator experiences feeling of resistance against the sin, fear of the sin and difficulty in committing the sin. Thirdly, during the process of committing the sin and as a result of sexual arousal, the perpetrator feels sexual pleasure, emotional enjoyment and a kind of primary pleasure, meanwhile the feeling of guilt turns all these pleasures into torture. Embarrassment, inquietude and fear (the fear of God torment and the sin revealing) are feelings of perpetrator during the process of sin commitment. After committing the sin, a sense of doubt and rethinking about the sin and then, inner pressures and regret appear. These pressures are revealed through unpleasant and strange feelings of inquietude, unfaithfulness, regret, being despised and feeling guilty back of one’s conscience. Feeling guilty back of conscience is the most common feeling which leads to repentance and self-justification to decrease these pressures. To recite the marriage vows, to state having sexual relations with the intention of marriage, and to hope to God’s forgiveness are among common justifications after committing the sexual sin. A last, sexual sin repetition normalizes sin and causes a decrease in guilty feelings, and an increase in sin pleasure, and finally it makes some changes in primary sexual beliefs and values.