This study assessed the effects of a model that integrated the theory of planned behavior (TPB) with extrinsic motivation (EM) in predicting the intentions of fifth-grade students to not use illicit drugs. A cluster-sampling design was adopted in a cross-sectional survey (N = 571). The structural equation modeling results showed that the model attained an acceptable overall fit and explained 85% of the variance in intention. The EM variables influenced intention through subjective norms and perceived behavioral control. Study findings support the proposed TPB-EM model and show that EM can foster a social cognitive mechanism that indirectly affects intention.