75% of teenage girls endured symptom of premenstrual syndrome. The lack of knowledge, experience, and information among teenage girls about premenstrual syndrome could aggravate the symptom felt so that it created anxiety. Anxiety that could happen in teenage girls among others: restlessness, cold sweat, fear, and various health problem that could disturb daily activities. Research Objective: The objective of the research was to find out the relationship between knowledge about premenstrual syndrome and the anxiety of teenage girls in facing premenstrual syndrome in Junior High School 1 of Kasihan, Bantul, Yogyakarta. Method: The kind of the research was non-experimental correlation descriptive with cross sectional method. The data were analyzed using statistic test of Sperman Rank. The population of the research was teenage girls in Junior High School 1of Kasihan, Bantul, with sample of 80 respondents. The sample collecting technique used Simple Random Sampling. The instrument in the research was questionnaire of knowledge about premenstrual syndrome and questionnaire of anxiety using questionnaire of Hamilton Anxiety Rating Scale (HARS). Result: The majority of the respondents had less knowledge on premenstrual syndrome i.e. 36 respondents (45%) and who endured heavy anxiety when having premenstrual syndrome were 25 respondents (31.2%). There was relationship between knowledge about premenstrual syndrome and the anxiety among teenage girls when facing premenstrual syndrome in Junior High School 1 of Kasihan with significancy value of p = 0.047 (< 0.05) and Pearson correlation value of r = 0.222) that showed positive correlation with low/ weak correlation level/ strength. Conclusion: There was significant relationship between the level of knowledge about premenstrual syndrome and the anxiety of the teenage girls when facing premenstrual syndrome in Junior High School 1 of Kasihan, Bantul.