Finland and Singapore are both top-performing countries in international assessments such as PISA. Finland has been consistently one of the high-achievers regarding not only students' literacy levels but also educational equity. Similarly, Singapore has continuously shown outstanding performance in PISA. It outperformed all the other participants in all three literacy domains in PISA 2015. We believe exploring the factors affecting students' science literacy in these two top-performing countries will provide the low-performing countries with a useful guideline. In this regard, we aim to build models including the student and school-level factors associated with the students' science literacy in Finland and Singapore using PISA 2015 data. We conduct Hierarchical Linear Modeling to create these models. The sample includes 5882 students in Finland and 6115 students in Singapore. The resulting models explain about 43% and 40% of the within-school variance while they explain 62% and 71% of the between-school variance in science literacy in Finland and Singapore respectively. At the student level, students' enjoyment and interest in science are the most influential predictors of science literacy while at the school level, schools' economic, social, and cultural status is by far the most powerful predictor of science literacy in both Finland and Singapore.