Purpose: This paper aims to introduce the extended qualitative content analysis (EQCA) method to integrate data-reducing and data-complicating research steps when conducting qualitative research on the United Nations and other international institutions. Design/methodology/approach: EQCA supplements the method of qualitative content analysis, which enables researchers to deal with large amounts of data, with two elements from grounded theory, which allow detailed analysis and interpretation of codes and sub-codes. The elements in question are axial coding and theoretical sampling. Findings: EQCA provides a method to generate middle-range theories by combining theoretical and empirical analysis to address and theorize the complex interactions between actors, structures and norms in international institutions. The value added by the proposed method is demonstrated with a case study of a United Nations intergovernmental working group in the issue area of business and human rights. Originality/value: Based on the concepts of interpretation and social causality, this paper contributes to the body of qualitative research that transcends the dichotomy between positivist and post-positivist approaches in the disciplines of international relations and international political theory.