In this study, it was aimed to investigate the factors affecting students' science achievement according to student science teachers. The survey model which is one of the quantitative research methods was used. The sample was consisted of total 606 student science teachers from four state universities in Turkey. The data were obtained by using the Questionnaire of Factors Affecting Students' Science Achievement (QFASSA). The data were analyzed by using the descriptive analyzing technique. The factors affecting students' science achievement were analyzed under five dimensions. The result of the study shows that the most important factors affecting student science achievement according to student science teachers are the items in the dimensions of teacher and curriculum. The results also indicates that the most important predictor of science achievement is "teaching the topics in a way that may arouse the students' curiosity" in the teacher dimension of QFASSA.