Background: The Scenario Test is recognised for its effectiveness in assessing the interactive aspects of functional communication in people with post-stroke aphasia (PWA). Aims: To develop a Japanese version of the Scenario Test (Scenario Test-JP) and assess its reliability and validity. Methods & Procedures: Among 66 participants, we selected 61 individuals: 34 PWA and 27 healthy controls (HCs). We modified the Scenario Test-JP based on the UK version and subsequently evaluated its reliability (internal consistency, test--retest and intra-rater and inter-rater reliabilities) and validity (convergent and discriminant) by comparing PWA and HCs. Outcomes & Results: The Scenario Test-JP showed strong reliability with a Cronbach's [alpha] of 0.93, test-retest reliability with an intraclass correlation coefficient (ICC) of 0.97, intra-rater reliability with an ICC of 0.95-1.00, and inter-rater reliability with an ICC of 0.96. The validity of the test was confirmed with concurrent scores ranging from [rho] = 0.37 to 0.76 (p < 0.05) and known-groups validity (p < 0.001, r = -0.56). Conclusions & Implications: The reliability and validity of the Scenario Test-JP align with those of the original Dutch version and the UK and Greek versions. Additionally, the assessment can now include extended alternative communication methods, such as digital devices, indicating the potential of the Scenario Test-JP for modern Japanese speech-language therapy.