Objectives <p>This study aimed to develop the Reflecting/Nonattachment Mindfulness Scale (RNMS) based on the Two-Dimensional Four-factor Model of Mindfulness (TFMM) and existing mindfulness scales, and to examine its reliability and validity.</p> Method <p>Participants were randomly recruited through the Credamo data collection platform to conduct item analysis and exploratory (<i>n</i>₁ = 465) and confirmatory (<i>n</i>₂ = 500) factor analyses and to examine the scale’s incremental validity and concurrent validity (<i>n</i>₃ = 476).</p> Results <p>The RNMS comprised four factors in exploratory factor analysis: reflecting self, reflecting external phenomena, nonattachment to self, and nonattachment to external phenomena. Confirmatory factor analysis indicated a good fit for the four-factor model. The Cronbach’s <i>α</i> for each factor was no less than 0.85, the average variance extracted for each factor was no less than 0.60, and the composite reliability for each factor was no less than 0.83. Openness to experience was significantly positively correlated with nonattachment to external phenomena (<i>r</i> = 0.72), mindful presence was significantly positively correlated with both reflecting self (<i>r</i> = 0.53) and reflecting external phenomena (<i>r</i> = 0.53), and insight was significantly positively correlated with reflecting self (<i>r</i> = 0.54) and nonattachment to external phenomena (<i>r</i> = 0.55).</p> Conclusions <p>The RNMS demonstrated good reliability and validity and can serve as a measurement tool for mindfulness research. The RNMS differentiates between experiential and environmental stimuli objects of awareness, thereby facilitating more precise measurement of specific components of mindfulness in future research. The RNMS also reveals differences among the various components of mindfulness; thus, mindfulness cannot be reduced to a unitary construct.</p>