The maturity model (MM) and Delphi research areas are extensive and diverse, leading to numerous approaches. This study addresses the Delphi method regarding its rigor requirements within the IS literature. To this end, the example of maturity model development is investigated. Hence, Delphi studies for MM development are identified and analyzed regarding their rigorous application and design. The examination focuses on the connections between maturity model aspects and the Delphi methodology. Hence, relevant aspects of maturity model and Delphi literature are elaborated, and criteria for methodological rigor are derived. A key challenge is linking the method to the specific design objective (in this study example, the development of a maturity model). After conducting a literature search to identify studies that use the Delphi method for MM development, these criteria are used as a basis for deductive content analysis. The results indicate a lack of clarity regarding the methodology, as different aspects are reported, although the general demands, starting points, and goals were similar. A need for design guidelines for planning and conducting Delphi studies is emphasized and addressed in this paper. Hence, guidelines for designing Delphi studies are developed and presented, considering relevant aspects for ensuring rigorous implementation. The focus lies on the linkage between study design and intended model elements, as this demonstrates the complexity of the study design and the relevance of the design decisions through an example. The guidelines integrate the different methodological aspects of maturity model development and the Delphi methodology, providing an orientation framework for the design process of such research projects. Therefore, this study contributes to existing research by proposing design guidelines for Delphi studies to foster rigor in the specific context of maturity model development. Although the presented guidelines focus on the maturity model context, the general design approach and decisions are transferable and applicable to other domains. Hence, this research contributes to the Delphi literature by providing insights into how relevant elements should be addressed in the designing process of a Delphi Study.