Objective: Impulsivity is an established etiological risk factor for alcohol- and cannabis-related outcomes. However, limited work has focused on longitudinal associations between multiple trait impulsivity facets and indices of alcohol and cannabis use among military veterans—a contextually distinct population that evidence unique impulsive personality traits and substance use patterns. Method: A structural equation model (SEM) examined longitudinal associations between five UPPS-P impulsivity facets measured at baseline and six indices of alcohol and cannabis use (i.e., frequency, quantity, and problems) measured at 1-year follow-up among 361 returning Operation Enduring Freedom, Operation Iraqi Freedom, and Operation New Dawn (OEF/OIF/OND) veterans. Results: Findings indicated baseline sensation seeking was significantly positively associated with 1-year alcohol use frequency (β = .18); baseline negative urgency was positively associated with alcohol use problems (β = .31); and baseline lack of perseverance (β = .25) and sensation seeking (β = .21) were positively associated with 1-year cannabis use problems. None of the baseline impulsivity facets were associated with 1-year alcohol use quantity, cannabis use frequency, or cannabis use quantity. Conclusions: Results provide preliminary support that impulsivity may play a unique role in understanding alcohol- and cannabis-related problems over time among veterans. Further, results suggest that specific impulsivity facets are prospectively associated with cannabis problems (i.e., lack of perseverance and sensation seeking) and alcohol problems (i.e., negative urgency). Findings reinforce the importance of differentially evaluating impulsivity-substance use associations within contextually distinct populations (e.g., adolescent, veteran), and highlight potentially meaningful intervention targets among veterans. However, replication is needed with stronger temporal controls and more diverse veteran subsamples. (PsycInfo Database Record (c) 2022 APA, all rights reserved)