The purpose of this research is to investigate the relationship between attachment styles (secure, avoidance, anxiety) and attitude toward marriage among the undergraduate students of Tehran University. The study is an applied research of correlation type. Based on statistical criteria, 388 persons were selected as the sample. After discarding the failed questionnaires, we analyzed 377 sheets. In order to collect data, we used Collins and Reads questionnaire of adult attachment, including eighteen questions of Likert scaling test, and premarriage inventory (PMI), including forty – five Yes/ No questions. Descriptive statistics (abundance, ratio, percentage, average, chart …) were used for data analysis, and inferential statistics (correlation and regression) were applied in order to test the research questions. The results indicated that there is a significant relationship between secure attachment style and attitude towards marriage, and that attitude toward marriage can be predicated by attachment score. However, there is no significant relationship between avoidance attachment style and anxiety attachment style with attitude toward marriage. In addition, there is no significant relationship between anxiety attachment style and attitude toward conflict resolution. But there is a meaningful relationship between secure attachment style and avoidance attachment style with attitude toward conflict resolution.