According to the 2010 Indonesia Population Census, 26.7% of Indonesia‘s population is aged 10 to 24. This large number clearly requires serious attention and treatment of all sectors responding to youth‘s issues. When young people have little information and knowledge about sexuality and reproductive health (SRH), they may not be able to protect themselves from risky behavior including premarital sexual intercourse. The negative impact may result in unwanted pregnancy and illegal abortions that endanger youth‘s lives. The objectives of the study are to investigate the relationship between cognitive factors (SRH knowledge and attitude toward woman‘s virginity) and premarital sexual intercourse among unmarried youth in Indonesia. The study employed secondary data of Indonesia Demographic and Health Survey 2012. A total of 10,861 unmarried men and 8,816 unmarried women aged 15 to 24 were selected for analysis. Premarital sexual intercourse is found to be more common among unmarried males (12.4%) compared to unmarried females (1.9%). SRH knowledge were significantly associated with premarital sexual intercourse among unmarried male, but conversely for unmarried female. Both unmarried male and female who agree that women should maintain virginity before marriage were less likely to have premarital sexual intercourse than who disagree. In addition, both unmarried male and unmarried female who agree that men still value women‘s virginity were less likely to have premarital sexual intercourse than those who disagree. The study indicates premarital sexual intercourse committed by unmarried youth in Indonesia is affected by cognitive factors. The findings suggest that SRH education should be provided formally in universities which focused on students aged 20 to 24.