This is a report of one case of a design and development research study that aimed to validate an overlay instructional design model incorporating the theory of multiple intelligences into instructional systems design. After design and expert review model validation, The Multiple Intelligence (MI) Design Model, used with an Instructional Systems Design (ISD) Model, was tested for use by four practicing instructional designers. Instruction developed for learners using this model was then evaluated measuring post-test and attitudinal scores with 102 participants. This report also provides a reflection on the lessons learned in conducting design and development research on model validation. The procedures and findings have implications for the processes involved in instructional design model validation through designer use and program implementation.