The present study examined whether five facets of mindfulness (acting with awareness, describing, observing, non-judging of inner experience, and non-reactivity to inner experience) relate to alcohol and cannabis outcomes (quantity of use and negative consequences) via delaying gratification. Participants were college students across seven universities who used alcohol (n = 1467) and/or cannabis (n = 647) in the last 30 days. For the alcohol analytic sample, the majority of students identified as being female (71.1%) and reported a mean age of 20.04 (Median = 19.00; SD = 3.47) years. For the cannabis analytic sample, the majority of students identified as being female (69.7%) and reported a mean age of 19.63 (Median = 19.00; SD = 2.85). Within our model, significant indirect effects were only found for two mindfulness facets. Specifically, the indirect effects from acting with awareness (alcohol indirect β = -0.026, SE = 0.006; cannabis indirect β = -0.019, SE = 0.008) and observing (alcohol indirect β = -0.017, SE = 0.005; cannabis indirect β = -0.015, SE = 0.007) to consequences via delaying gratification and quantity were significant for both the alcohol and cannabis models, such that acting with awareness and observing were associated with higher delaying gratification; which in turn was associated with lower quantity of use, which in turn was associated with fewer consequences for both the cannabis and alcohol models. Our findings suggest that delaying gratification is important to understanding the relationship between specific mindfulness facets (i.e., acting with awareness and observing) and alcohol and cannabis outcomes. Mindfulness interventions aimed at reducing substance use may benefit from targeting delaying gratification through increasing acting with awareness and observing.