This article presents the development and validation process of a qualitative data collection instrument aimed at analysing Natural Sciences teachers’ perceptions of practical work in lower secondary education (third cycle) in Portugal. The methodological approach combined a systematic literature review following PRISMA guidelines with an analysis of relevant curricular frameworks and legal documents. Based on the triangulation of these sources, a semi-structured interview guide was constructed, validated by a panel of five experts from four Portuguese public universities, and tested through a pilot interview. The final instrument comprises seven dimensions and fourteen subdimensions, totalling 44 items. It demonstrated methodological rigour and practical applicability for qualitative data collection and analysis. Findings indicate that the instrument enables a comprehensive exploration of teachers’ practices and perceptions regarding practical work, offering a valuable contribution to the research on didactics of science and to the professional development of teachers.