Inquiry and facilitated dialogue are two tools that interpreters can use to engage visitors. Professional development focused on the topics of interpretation, inquiry, and facilitated dialogue presents interpreters with relevant knowledge and skill practice. Knowledge and skill practice are thought to increase confidence and contribute to more effective interpretation. However, there is a general lack of understanding of the benefits of professional development in these focus areas. Therefore, this three-phase, quasi-experimental, sequential explanatory mixed methods study aimed to learn more about the immediate and longer-term effects of experiential professional development focused on facilitated dialogue and inquiry-based interpretation techniques on confidence, knowledge, and practice of interpreters at informal and nonformal nature-based interpretive education sites. Additional exploratory questions were focused on motivations to do interpretation and to participate in professional development, and relationships between interpreter goals and effective interpretation. The paradigm under which this research was conducted was postpositivism and social constructivism, with a critical realism ontology and subjective epistemology. Aligning with the hypotheses, content knowledge and skills increased for participants immediately following professional development, and participants felt more confident regarding their knowledge and ability to incorporate content and skills into their professional practice. This level of confidence remained the same nearly a year after attending the workshop. Overall, participants are intrinsically motivated to be an interpreter. Removing or reducing perceived barriers to integration and implementation of new skills and techniques acquired from professional development will likely lead to more interpreters applying these skills and techniques.