Background: Although the reasons behind tobacco smoking at young age are complex, research has identified curiosity as a potent driver of smoking among adolescents. Objective: The objective of the current study is to develop and provide initial evidence of reliability and validity of a short scale assessing smoking curiosity among adolescents (first measure of its kind). In particular, we developed and tested the adolescent smoking curiosity scale (ASCOS). Methods: After scale development, 101 adolescents completed a survey on smoking-related measures, including ASCOS (June to August 2014). We conducted exploratory factor analysis and Cronbach's alpha calculation to inspect factor-structure and reliability. We conducted multiple linear regression models to examine the scale's capacity to predict antecedents of smoking initiation. Results: Factor analysis supported a single-factor structure of smoking curiosity. ASCOS was internally reliable (Cronbach's alpha = 0.83). Controlling for demographics, the measure correlated significantly with temptation to try smoking (beta = 0.41, p < 0.01), number of friends who smoke (beta = 0.27, p < 0.01), agreeing with the pros of smoking (beta = 0.41, p < 0.001), sensation seeking (beta = 0.21, p < 0.05), and depression (beta = 0.23, p < 0.01). When controlling for a single-item measure for smoking curiosity, ASCOS significantly predicted susceptibility to smoke cigarettes (OR = 3.40, p < 0.05) and cigars (OR = 6.66, p < 0.01). Conclusions: ASCOS presented good psychometric properties and passed initial validity-testing through associations with antecedents of smoking. ASCOS was a better predictor of susceptibility to smoke than did a traditional single-item measure used by previous research. As an implication, ASCOS can be crucial to the development of tailored interventions for smoking prevention that can reduce smoking curiosity.