This study uses nudging theory to develop and validate a measure for self-nudging toward physical activity. The research unfolds in three phases: (a) initial item development through interviews and literature review, (b) psychometric testing with Japanese employees (N = 1540), and (c) validity assessment in a longitudinal subsample (N = 716). Factor analyses confirm a reliable one-factor structure. The scale demonstrates content and predictive validity, showing positive relationships with physic