The aim of this study was to investigate the relationship between students' Academic Self-Concepts and certain demographic variables (gender, location of school, type of family, medium of study and type of school) and the relationship between academic self-concepts and students' achievement in the course of Science. The study was carried out with high school students (N=235). In the study, the data were collected through the Academic Self-Concept scale (the reliability coefficient of the scale was calculated by the researchers as 0.89), achievement scores in the course of science and a questionnaire for the demographic information’s of the participants. Descriptive statistics, t-test, Correlation analysis, were used to analyze the data. The analysis of the data revealed that no significant relationships and differences were found in students’ academic self-concepts with respect to gender, school location, type of the family and type of school. In the study, positive relationships were found but low between students’ achievement in the course of science and the Academic Self-Concept.