Posttraumatic stress disorder (PTSD) and alcohol use disorder (AUD) are highly comorbid with complex and often unclear associations. Working memory deficits may represent a shared mechanism implicated in emotion regulation and control over impulsive alcohol use. Here we test whether PTSD symptoms and working memory correlated with performance on a behavioral economic assessment of alcohol demand. 113 veterans (mean age 51 years; 89% male) completed an Alcohol Purchase Task (APT) and were assessed for PTSD, alcohol use, and working memory. We examined the interaction of PTSD symptoms and working memory on four indices of alcohol demand measured from the APT; specifically, we used separate models to test whether associations between working memory and intensity (consumption at $0), Omax (maximum expenditure), Pmax (price at maximum expenditure), and elasticity (price sensitivity), differed as a function of PTSD symptoms. In a model controlling for hazardous drinking, average drinking levels, age, sex, marital status, occupation, and education, we observed a significant interaction between PTSD symptoms and working memory on elasticity, whereby greater working memory capacity was associated with greater elasticity for veterans with lower PTSD symptoms. Follow-up analyses regarding specific PTSD symptom domains indicated that this effect was strongest for avoidance symptoms. Taken together, working memory abilities correlated with subjective valuations of alcohol in a laboratory setting for veterans with less severe PTSD symptoms. This work highlights the conditions under which working memory may be a potential target for interventions geared toward reducing alcohol use in veterans with co-occurring PTSD and AUD. (PsycInfo Database Record (c) 2021 APA, all rights reserved).