This article explores the usefulness of detective role-play as a research method to facilitate young children's critical thinking. The study examines four specifically designed detective play experiences, adopting an ethical rights-based approach to research with children. This qualitative multiple-case study is grounded in play-based pedagogy within a social-constructivist theory. The study consists of four exploratory cases focusing on semi-structured mystery play experiences. Twenty-four children aged 5-6 years participated. Child-centred and pedagogically appropriate methods and tools were used to facilitate the voice and visualisation of children's thinking. Conducting observations (direct and video recorded) was effective in capturing the different ways young children expressed their thinking. Findings show that engaging in investigative collaborative enquiry, dazzling children's curiosity, empowering children, listening to and acknowledging children's thinking, and guiding and scaffolding were useful for facilitating critical thinking skills and dispositions. Additionally, the consideration of design elements, such as the degree of structure, open-endedness and content knowledge dependency, was found essential for creating productive spaces for facilitating children's thinking. For example, an open approach to a task is beneficial for an open-natured exploration of critical thinking, while a more structured and adult-controlled design is more effective for facilitating and developing specific skills or dispositions.