Leadership research has a long history of a quantitative approach and it remains the most commonly used approach among leadership researchers. Researchers in a variety of fields have been applying mixed methods designs to their research as a way to advance theory. Mixed methods designs are used for collecting analyzing and mixing both quantitative and qualitative data in a single study or series of studies to both explain and explore specific research questions. This article provides a review of the basic characteristics of mixed methods designs. A broad series of leadership approaches is offered to help emphasize how the application of mixed methods designs have already been applied and where they might be directed in future research. Our review of articles published in the Leadership Quarterly between 1990 and June 2012 revealed a slight occurrence of existing application of mixed methods designs to leadership research. Of the articles reviewed only 15 studies were found to represent mixed methods research according to our conceptual framework. The overall intent of this article is to highlight the value of purposeful application of mixed methods designs toward advancing leadership theory and/or theoretical thinking about leadership phenomena.