The current trend in science curricula is to adopt a context-based pedagogical approach to teaching. New study materials for this innovation are often designed by teachers working with university experts. In this article, it is proposed that teachers need to acquire corresponding teaching competences to create a context-based learning environment. These competences comprise an adequate emphasis, context establishment, concept transfer, support of student active learning, (re-)design of context-based materials, and assistance in implementation of the innovation. The implementation of context-based education would benefit from an instrument that maps these competences. The construction and validation of such an instrument (mixed-methods approach) to measure the contextbased learning environment is described in this paper. The composite instrument was tested in a pilot study among 8 teachers and 162 students who use context-based materials in their classrooms. The instrument’s reliability was established and correlating data sources in the composite instrument were identified. Various aspects of validity were addressed and found to be supported by the data obtained. As expected, the instrument revealed that context-based teaching competence is more prominently visible in teachers with experience in designing context-based materials, confirming the instrument’s validity.