Posttraumatic stress disorder (PTSD) confers considerable risk for alcohol-related harms. Trauma-exposed individuals may turn to alcohol in response to intrusive trauma-related symptoms (e.g., memories, flashbacks, nightmares) or distressing trauma-related emotions, with such desires to drink shifting dynamically in-the-moment in response to PTSD symptoms. However, the in-the-moment reasons for drinking that may underlie these dynamic processes remain largely unknown. The present qualitative study aimed to identify key in-the-moment PTSD-related reasons for drinking. Focus groups of frequent drinkers with a provisional diagnosis of past-month PTSD recruited from the community ( = 39; 44% female adults) provided in-depth information on their reasons for drinking during several recent drinking episodes. Focus group data were subjected to directed content analysis. Findings revealed several novel insights regarding in-the-moment reasons for PTSD-related drinking. Participants endorsed perceptions that alcohol could numb trauma-related thoughts and emotions or distract from intrusive symptoms (i.e., negative reinforcement). Participants also described perceptions that alcohol could enhance positive emotions amid persistent negative mood and help process complex trauma-related memories as well as facilitate interpersonal connection. Results identify specific, in-the-moment reasons for drinking in response to emergent PTSD symptoms, which appear at times unique from more general drinking motivations. Findings shed light on potential risk pathways for problem drinking in response to PTSD symptoms as they occur across daily life. These specific in-the-moment reasons for drinking could represent important clinical targets for real-time, adaptive interventions for comorbid PTSD and problem alcohol use.