Reflective activity (RA), the ability to maintain an awareness of oneself and the situation while interacting in the situation, is a human quality receiving increasing attention in the literature on adaptation and adjustment. However, standardized measures assessing this ability have been lacking. The reflective activity measure was designed to capture individual differences along a continuum ranging from excessively preoccupied and inactive, to reflectively active, to thoughtlessly reactive or impulsive. The RA scale assesses the four dimensions of: (1) reflection, (2) action, (3) information gathering, and (4) over-absorption, with regards to facing problematic situations. To confirm the factor structure of the scale, factors analyzes were conducted using an oblique rotation. The relationships among the four RA dimensions were established with Pearson correlations, internal consistency was established with alpha reliability coefficients, test-retest reliability was confirmed by the Pearson product-moment method, and construct validity was confirmed with correlational analyses of each RA dimension with measures of analogous or antithetical constructs (Buss-Plomin Impulsivity Scale; Self-Consciousness Scale; and Action, Feelings, and Deliberation facets of the NEO Personality InventoryRevised). This paper presents the validity and reliability data of the RA scale (N = 421) and the relevance of the reflective activity construct to addiction and mental health.