Qualitative research and its methods stem from the social sciences and can be used to describe and interpret complex phenomena that involve individuals' views, beliefs, preferences, and subjective responses to places and people. Thus, qualitative research explores the many subjective factors that may influence patient outcomes, staff well-being, and healthcare quality, yet fail to lend themselves to the hypothesis-testing approach that characterizes quantitative research. Qualitative research is valuable in the intensive care unit to explore organizational and cultural issues and to gain insight into social interactions, healthcare delivery processes, and communication. Qualitative research generates explanatory models and theories, which can then serve to devise interventions, whose efficacy can be studied quantitatively. Thus, qualitative research works synergistically with quantitative research, providing new impetus to the research process and a new dimension to research findings. Qualitative research starts with conceptualizing the research question, choosing the appropriate qualitative strategy, and designing the study; rigorous methods specifically designed for qualitative research are then used to conduct the study, analyze the data, and verify the findings. The researcher is the data-collecting instrument, and the data are the participants' words and behaviors. Data coding methods are used to describe experiences, discover themes, and build theories. In this review, we outline the rationale and methods for conducting qualitative research to inform critical care issues. We provide an overview of available qualitative methods and explain how they can work in close synergy with quantitative methods. To illustrate the effectiveness of combining different research methods, we will refer to recent qualitative studies conducted in the intensive care unit.