Background: PCOS is one of the primary causes of infertility, and it is a major problem among adolescents. Education is one of the most widely adapted strategies for health promotion. So, it is important to teach about polycystic ovarian syndrome among adolescent girls to identify the early signs of PCOS. The aim of the study was to assess the effectiveness of a planned teaching program on knowledge regarding polycystic ovarian syndrome among adolescent girls. Design: A one group pretest posttest research design was utilized for the current study. Sample: A simple random sampling technique was used carried out among 65 adolescent girls at Um Salama High School in Al-Ahsa. Tools of Data collection; Structured Questionnaire was utilized for the research. SPSS version 20 was used for data analysis Result The study findings shows that there were 52.31% of them had inadequate knowledge, 24.62% of them had moderately adequate knowledge, and 23.07% had an adequate level of knowledge regarding PCOS in pretest. In the posttest, 1.54% of them had inadequate knowledge, 3.08% had moderately adequate knowledge, and 95.38% had an adequate level of knowledge regarding PCOS. The results show that organized education was successful in educating teenage girls about polycystic ovarian syndrome (paired t'= 9.61, p<0.05). Conclusion; The study findings concluded that the teaching regarding PCOS was more effective for adolescent girls. Recommendation: Through this research, the investigator recommends to raise awareness of PCOS through planned teaching program for the adolescent girls in schools.