Children who have been exposed to a natural disaster in their lifetime comprise a significant population with specific risks and vulnerabilities related to their disaster exposure. The risk of experiencing these problems may be particularly enhanced for at-risk youth who may have unique needs in instances of disaster or emergency. The goal of the current study was to examine the role that severity of disaster exposure plays in determining the timing of substance use initiation (cigarettes, alcohol, marijuana) and the frequency of use four years later in a sample of at-risk, aggressive youth exposed to a devastating tornado. Of further interest was an examination of temperamental (fear and inhibitory control) and social variables (peer victimization) that may moderate the effect of disaster exposure as it predicts substance use initiation and frequency. Results indicated that disaster exposure severity was predictive of increases in the use of some substances four years after the tornado, but exposure alone was not predictive of initiation. Instead, the effects of exposure severity were dependent on levels of temperamental fear, with exposure severity predicting increases in risk for alcohol use initiation only for youth high in fear. Additionally, greater levels of inhibitory control protected youth from earlier alcohol use initiation. However, while greater levels of inhibitory control and fear individually protected youth from substance use, the combination of greater inhibitory control and fear predicted increases in frequency of alcohol use. Peer victimization was also predictive of later substance use frequency but did not predict earlier initiation. Findings highlight a need to research the initiation and frequency of use for substances individually, while also assessing the needs of youth exposed to natural disasters with both their degree of disaster exposure and specific temperamental and social characteristics in mind