The objectives of this study were to 1) examine longitudinal predictors of JUUL and other tobacco product initiation, 2) compare these predictors across product type, and 3) describe cross-sectional characteristics of JUUL initiators, among a cohort of Texas adolescents. Analyses were also stratified to examine whether predictors of initiation differed by susceptibility to tobacco use at baseline. This study utilized data from Waves 7 and 8 (Fall 2017 and Spring 2018) of the Texas Adolescent Tobacco and Marketing Surveillance System (n = 2272). Chi-square tests and multinomial logistic regressions were conducted to examine differences in predictors of initiation. Among those who initiated at Wave 8 (n = 107), 40.2% initiated JUUL, 43.9% initiated other ENDS, and 15.9% initiated other combustible tobacco. For the full sample, ever marijuana use predicted the initiation of all tobacco products (Relative Risk Ratios "RRRs" from 2.31-4.13) as compared to non-users. For non-susceptible youth, ever marijuana use significantly predicted the initiation of JUUL (RRR = 10.08, 95% CI = 2.11-48.17) and other ENDS use (RRR = 12.07, 95% CI = 2.97-49.04). Peer tobacco use predicted the initiation of JUUL (RRR = 3.06, 95% CI = 1.38-6.81) and other ENDS use (RRR = 5.36, 95% CI = 2.11-13.64) for the full sample, as well as those who were susceptible to tobacco use. For non-susceptible youth, peer tobacco use predicted the initiation of combustible tobacco use (RRR = 16.56, 95% CI = 1.56-175.84). Prominent reasons for JUUL use included curiosity, friend use, and less harmful that cigarettes. Results highlight the role of marijuana in the initiation of all tobacco products, even among low-risk youth; other predictors varied between product type. Interventions should address specific predictors to prevent youth from transitioning to tobacco use.