The author sought to investigate the effects of inquiry-based science instruction on science achievement and interest in science of 5,120 adolescents from 85 schools in Qatar. Results of hierarchical linear modeling analyses revealed the substantial positive effects of science teaching and learning with a focus on model or applications and interactive science teaching and learning on science achievement and interest in science. In contrast, science teaching and learning using student investigations and hands-on activities had substantial negative effects on science achievement in the context of other variables. Implications of the findings for educational policy and classroom practice are discussed. (Contains 3 tables.)