In this study, we use face and content validity to determine whether a modified game-based testing instrument is appropriate and relevant for quantifying preschool children's emotional, cognitive, and attitudinal affinity with nature. Six environmental psychology experts completed a questionnaire and subsequent interviews with three of them provided insight into whether the features of the tool can measure a child's affinity with nature. Interrater agreement and content validity indexes establish whether the instrument meets four established validation criteria: clarity; ease of use; appropriateness; and relevancy. Results indicate that the modified device does not measure the original core concept: affinity with nature, and that face and content validation outcomes do not yield acceptable outputs. As a result, the foundation and key characteristics of the instrument were revised to enhance its ability to produce trustworthy results and more accurately measure the revised core concept of connection to nature and environmental knowledge.