Anxiety and self-efficacy are among the factors that impact students' performance in biology. The current study aims to investigate high school students' perception of biology anxiety and self-efficacy, in relation to gender, grade level, interest in biology, negative experience associated with biology classes, and teachers' approaches in the class. The research was designed as a survey model. The study group consisted of 160 students in 9th, 10th, and 11th grades at 4 different high schools in Ankara during 2014 Spring Semester. Biology Anxiety Scale and Biology Self-Efficacy Perception Scale, both developed by the researchers, were used as data collection tools. Data were analyzed through t test, ANOVA, and Pearson Correlation in SPSS software package. The research results show that interest in biology and negative past experience were significant predictors of students' biology anxiety and that students' biology self-efficacy percepts significantly differed on gender, grade level, interest in biology, past experiences, and teachers' approaches in the classes. Considering the relationship between anxiety and self-efficacy, activities must be organized at schools in order to reduce students' biology anxieties.