This dissertation was driven by a lack of evidence substantiating the current state of visual literacy knowledge and skills of instructional design professionals and the continuing call for visual literacy assessment research. The project has contributed two manuscripts that examine the existing visual literacy assessment research and document an attempt at designing and developing an evidence-based visual literacy assessment product. The first manuscript, a comprehensive literature review, offers insights into how visual literacy has been assessed over the years and the challenges associated with establishing a research agenda for visual literacy assessment as revealed by current research and practice. The second manuscript, adopting the design and development research methodology, aims to design and develop a product that instructional designers can use to assess or diagnose the strengths and weaknesses in their knowledge regarding a fundamental vocabulary of visual literacy. / Doctor of Philosophy / Learning and training design professionals are often expected by the job market to communicate effectively using static or moving visual messages throughout the learning or performance problem-solving process. This process typically includes the analysis of the problem and the design, development, implementation, and evaluation of the corresponding solution. However, research has reported a mismatch between employers' and employees' perceptions of the visual competencies of learning and training professionals. Moreover, there is very limited evidence-based research assessing these visual competencies or producing assessment products or procedures. Therefore, this dissertation has contributed two manuscripts to address this issue. In the first manuscript, a comprehensive review of the relevant literature is presented to inform how these visual competencies have been assessed by previous efforts and to identify the difficulties or challenges associated with the assessment as revealed by the researchers and their work. The second manuscript designed and developed an open-access digital product for learning and training professionals to assess or diagnose their knowledge of a collection of foundational terms and concepts that underpin many visual competencies. Therefore, this product helps learning and training professionals to remediate their visual knowledge accordingly. As part of the design and development process, a group of learning and training professionals and another group of visual competency experts experienced the product and provided valuable feedback that has guided product modifications and identified areas for future development.