Objectives: This study aimed to identify the determinants associated with 4 smoking trajectories (never smoking, current smoking, consistently quitting smoking, and smoking relapse) among Indonesian children using pooled national data. Methods: This study analyzed children’s smoking trajectories using pooled data from the Indonesian Global Youth Tobacco Survey (2006, 2009, 2014, and 2019). Multinomial logistic regression was applied to examine 4 categories of smoking behavior, and propensity score matching (PSM) was used to address potential selection bias related to advertising exposure. Results: Higher prices (>IDR31 000/USD1.87) (relative risk ratio [RRR], 0.527) were protective against relapse. This policy effect was systematically undermined by single-stick purchasing, which increased relapse risk by 57.41 times (p<0.01). Peer smoking (RRR, 3.696) and exposure to advertisements in sports events (RRR, 1.477) were also significant risk factors for relapse. Free cigarette distribution demonstrated the strongest association, corresponding to a 23.1 percentage-point increase in relapse probability. Conclusions: The findings indicate that children’s smoking relapse in Indonesia is shaped by distinct behavioral trajectories. Relapse was influenced by the widespread availability of single-stick cigarettes, pervasive marketing, peer dynamics, and relatively affordable prices. These results underscore the urgent need for a comprehensive strategy that includes substantially increasing excise taxes, eliminating single-stick sales, and fully banning tobacco advertising. Simultaneous implementation of these measures is crucial to prevent relapse and interrupt the progression toward lifelong nicotine addiction. © 2026 The Korean Society for Preventive Medicine.