This study aimed to investigate extent to which variables directly related to science, which are found in Programme for International Student Assessment (PISA) 2015 survey predicted literacy performance of students in Turkey and Singapore samples and determine differences and similarities between samples of two countries. The study used relational screening model. The study sample consisted of a total of 9680 students at age of 15, which included 4643 students from Turkey sample and 5037 students from Singapore sample. Also, sample included 177 schools from Turkey and 163 schools from Singapore. The study used Hierarchical Linear Modeling (HLM) statistical technique, which is appropriate for hierarchical data because school and student-level variables were together in study. According to findings of study, literacy performance indicated a significant difference between schools for both countries. However, approximately 52% of difference in students' literacy scores for Turkey sample and 34% for Singapore sample were found to stem from differences between schools. Student-level interest in science, research-based teaching and learning practices, teacher support in lessons, self-efficacy, teacher-centered teaching variables, and proportion of teachers at school level were determined to be a significant predictor of literacy in both countries. However, variables which are significant predictors of literacy were found to be the enjoyment of science for Turkey and the disciplinary climate in courses variable for Singapore. On other hand, proportion of teachers with an undergraduate education of four years or more, which is one of school-level variables, was found to be not a significant predictor of literacy performance fro both countries.