This study is conducted to describe the development of a theory-based instrument ”Optimal Experience” scale, which can be used to assess the experience in both sports and leisure activities. After the conceptualization and operational definition of the ”Optimal Experience”. Finally, the evidence shows that the ”Optimal Experience”24 items scale's reliability, factor structure, and validity analysis can measure the experience. The result of this study, also shows the ”Optimal Experience” scale for assessing both sports and leisure activities is a beneficial instrument for both references and applications.