This article addresses the absence of a validated psychometric instrument for measuring quiet quitting among employees, a phenomenon that gained mainstream attention following a viral TikTok post in July 2022 and whose prevalence reportedly increased after the COVID-19 pandemic. The authors argue that a reliable and valid scale is necessary to identify quiet quitters, understand the phenomenon empirically, and inform organisational interventions. The study followed a structured instrument development process: item generation via literature review and employee interviews, expert content validation, cognitive interviews, pilot testing for face validity, item analysis, and exploratory and confirmatory factor analysis on a convenience sample of 922 Greek employees. The resulting Quiet Quitting Scale (QQS) is a nine-item, three-factor instrument measuring detachment, lack of initiative, and lack of motivation. Cronbach's alpha and McDonald's omega both exceeded 0.80, CFA fit indices were acceptable, and concurrent validity was confirmed through statistically significant correlations with burnout, job satisfaction, and turnover intention measures. The authors conclude that the QQS is a brief, reliable, and valid tool, while acknowledging limitations including a convenience sample drawn exclusively from Greece, potential social desirability bias in self-report data, and the absence of an established cut-off score. Key insights: Quiet quitting is operationalised as a three-dimensional construct comprising detachment, lack of initiative, and lack of motivation, distinguishing it conceptually from both active turnover and burnout. The QQS demonstrated statistically significant positive correlations with burnout measures (CBI and SIB) and turnover intention, and a negative correlation with job satisfaction, supporting concurrent validity. The study fills an explicit measurement gap: despite the prevalence of quiet quitting discourse and related constructs in the literature, no prior validated instrument existed specifically for this phenomenon. Practical takeaways: Organisations and researchers now have access to a brief, nine-item instrument with documented psychometric properties that can be used to screen for quiet quitting in workplace surveys. The scale's three-factor structure suggests that quiet quitting manifests across distinct behavioural and attitudinal dimensions — detachment, lack of initiative, and lack of motivation — which may inform differentiated diagnostic or monitoring approaches.