This research examines the relationship between high school teachers' understanding and reported practices of inquiry-based pedagogy (IBP) in science classrooms in Nigeria. A sample of 11 science teachers from an education district in Lagos, Nigeria, was chosen for this case study. Data were collected using a semi-structured questionnaire, which combined closed Likert-scale items (analysed using descriptive statistics) with open-ended questions assessing understanding and reported practices of inquiry in science classrooms, supplemented by semi-structured interviews (analysed using content analysis) with sampled teachers. Teachers' understanding of inquiry-based pedagogy was categorised into four clusters: teacher asks questions, students respond; teacher sets questions, students engage in project activities; teacher sets the context, students generate questions; and teacher sets the context, students generate questions and conduct investigations. However, responses to Likert scale items within each of the four clusters revealed patterns of reported practices that were unrelated to teachers' understanding of IBP. Although teachers within the same cluster shared a similar understanding of IBP, their reported practices varied owing to factors such as time constraints, overcrowded classrooms, teachers' beliefs, insufficient provision and utilisation of technological resources, as well as ineffective professional development for inquiry teaching methods.