Divorce as one of the social harms, has adverse influences on family inherence and social insecurity. Existing scientific evidence reveals an increase trend in the two social phenomena’s of divorce and premarital heterosexual relationships among young people. This paper is based on a mix method study conducted in 2011 and aims to assess the association between premarital heterosexual relationships and divorce. In the first phase of the study, 2031 female and male college students aged 18-40 years were selected using stratified cluster sampling from among 7 universities in Tehran (private and government). In this paper, 265 married students (12%) were compared with the data of 92 university educated men and women aged 18-40 who were about to separation (divorce) and attended to the two Family Courts in Tehran. Participants in Phase 2 were selected using simple sampling method. Data of married students (n=265) from the first phase were merged with the data of men and women who were about to divorce (n=92) at the analysis stage. Because, common questions were answered by respondents in phase 1 and 2, common data were merged and were analyzed. Results showed premarital heterosexual relationships among university educated men and women who intended to divorce was significantly greater than among married college students. Logistic regression showed that crude probability of divorce was 3.18 times greater among those who had experienced premarital intimate and sexual relationships with their current spouse compared to those without such relationships. The probability of divorce among those who reported intimate and sexual relationships with non-spouse, 3.63 times was greater than those without such relations. After control of factors related to divorce (e.g., compatibility with spouse, family confirmation of the spouse, divorce in the first degree family members), the probability of divorce was significantly associated with intimate and sexual relations with spouse and non-spouse before marriage (OR=5.03, P<0.01, and OR=4.27, P<0.01, respectively).