Purpose: The purpose of this study was to examine the state of unmarried cohabitation and to compare the differences of loneliness and family function among university students with cohabitation experience and those with no experience in Korea. Methods: A convenience sample of 213 university students was recruited from three universities located in G city and the Chonnam area of Korea. Data collection methods included: (a) a demographic questionnaire, (b) a questionnaire related to cohabitation, (c) UCLA scale: 20 items on a 4-point scale (c) Family APGAR questionnaire: 5 items on a 3-point scale. SPSS/WIN 17.0 was used for descriptive analysis, ${chi}^2$ test, t-test, and Pearson correlation. Results: In this study, 21.1% of the subjects had experiences of unmarried cohabitation. The cohabitation experience was related to gender, age, and monthly income. There was significant differences in family function between the two groups. Loneliness scores were significantly correlated with family function scores in the non-cohabitation group. Conclusion: To improve sex life of the university students, healthcare providers including school nurses may consider family function.