Abstract Background Reading and reading comprehension are crucial skills, yet many students in grade 4 struggle with them. To address this, several instructional practices have gained popularity. For one, explicit reading strategy instruction (ERSI) is deemed useful, given the finding that successful readers tend to employ reading strategies. As a second example, differentiated reading instruction (DRI) is believed to improve all students’ reading comprehension. Indeed, a one-size-fits-all approach may not work for all students, considering their different reader profiles. Despite the importance of ERSI and DRI, much uncertainty remains about what happens in the classroom and why. One way to understand teacher instructional practices such as ERSI and DRI, is by applying psychological behavioural theories to the teaching context. They provide a framework to predict human behaviour based on human characteristics and beliefs. Educational research points to teachers’ self-efficacy (TSE) and attitudes (TA) as particularly important concepts, especially in the field of science. However, associations between TA, TSE, instructional practices and students’ reading achievement remain insufficiently studied. This study addresses this knowledge gap by exploring the interplay between TSE and TA regarding ERSI and DRI, the implementation of these practices, and students’ reading achievement. Methods DigitalPIRLS 2021 data from Belgium (Flanders) were used. To gather information about ERSI, DRI, TA and TSE, national adaptations were made to the teacher questionnaires. Three nested path models with a two-level design (students nested into classes) were estimated. Results This study indicates that teachers with higher TSE and more positive TA in ERSI and DRI implement these practices more frequently. Positive TA regarding ERSI and DRI also correspond to positive TSE regarding these instructional practices. Furthermore, ERSI and DRI implementation are positively related. Finally, no significant associations between teacher beliefs, instructional practices, and students’ reading comprehension were found. Conclusion Whereas TSE and TA are considered highly context-dependent, uncertainty remains about TSE and TA regarding ERSI and DRI. The results highlight the importance of subject-specific TSE and TA for teachers’ instructional practices. Ultimately, the findings emphasize the necessity of supporting teachers in developing their TSE and TA towards reading comprehension instruction.