The aim of this study was to examine the effects of inquiry-based learning approach and emotional intelligence on students' science achievement levels. Within a quasi-experimental research design (pre and post-test), the sample of the research comprised of 56 grade 7 students drawn from two classes at different schools in Binjai, Indonesia. In analyzing data, descriptive and inferential statistics through twoway ANOVA were used. The results of research revealed that the students, who attended inquiry learning approach (experimental group), acquired the highest science achievement. For the students with high emotional intelligence, the students, who were taught with the inquiry-based learning approach, possessed higher science achievement than did the conventional learning approach (control group). For the students with low emotional intelligence, the students, who were exposed to the conventional learning approach, had higher science achievement than did the experimental group. The results showed an interaction between the effects of learning approach and emotional intelligence on science achievement. Teachers need to use inquiry-based learning so that students' science achievements can be improved. In order for effective inquiry-based learning, the emotional intelligence of students needs to be improved.