To improve the quality of education, the Kuwaiti Ministry of Education has encouraged schools to implement inquiry-based instruction. This study identifies psychosocial factors that predict teachers’ intention to use inquiry-based instruction in their science classrooms. An adapted model of Ajzen’s (1985) theory of planned behaviour—the Science Adoption Model—was used to study Kuwaiti science teachers’ beliefs. Four hundred and ninety-six teachers from all the government primary schools in Kuwait completed a questionnaire. The data were analysed using the Statistical Package for the Social Sciences (SPSS) to statistically examine the relationships among the constructs of the model. It was found that teachers’ attitudes towards using inquiry-based instruction significantly predicted their capacity to create and deliver inquiry-based lessons. Although Kuwaiti science teachers held positive beliefs about the implementation of inquiry-based instruction, many factors limited their use of this approach in their science classroom. One clear implication from this study is that educators need to overtly consider teachers’ beliefs as inquiry-based instruction reform is implemented.