Qualitative research methods, defined as the collection and analysis of non-numerical data to understand concepts and experiences, are often used to inform mental health practice and policies. When utilising qualitative research methods, it is important that the researcher uses an explicit theoretical framework to guide the study. A theoretical framework informs how researchers engage with a topic or problem, report on their work with participants, describe key concepts and address assumptions within the research questions and procedures. In this article, we describe the basic concepts underpinning three of the most commonly used frameworks in mental health research: positivism, interpretivism and critical realism. We also describe how these theoretical frameworks may guide the qualitative process, including the theoretical and methodological approaches chosen and the ways in which these theoretical frameworks can be applied in practice. To enhance understanding of these frameworks, we include examples of how such frameworks can be used in qualitative mental health research.