AbstractBackgroundUnderstanding the decision factors that drive harmful alcohol use among young adults is of practical and theoretical importance. We apply fuzzy‐trace theory (FTT) to investigate a potential danger that may arise from the arguably correct notion that a single drink carries no meaningful risk. Decisions that are mentally represented as one drink at a time could contribute to excessive drinking.MethodsCollege students (N = 351) made a series of decisions to take or decline eight hypothetical drinks presented one at a time. Outcome measures included each decision, recent alcohol consumption (weekly drinks, peak blood alcohol content, and binges), and alcohol‐related harms (scores on the Brief Young Adult Alcohol Consequences Questionnaire and Alcohol Use Disorders Identification Test). Linear regression models predicted each outcome from sex, perceived risk of a single drink, perceived risk of heavy drinking, perceived consequences of drinking, and general health‐related risk sensitivity.ResultsConsistent with FTT, decisions to have a first drink and up to four additional drinks in short succession were each associated with lower perceived risk of one drink—a “just‐one drink” effect—independent of perceived risks of heavy drinking, perceived consequences of drinking, and general risk sensitivity. Similarly, all measures of recent alcohol consumption and consequent harms were associated with perceived risk of one drink. Participants reporting “zero risk” of a single drink had worse outcomes on all measures than those reporting at least “low risk.”ConclusionsResults are consistent with the theoretically informed premise that consumption decisions are typically made one drink at a time rather than by deciding the total number of drinks to be consumed in a sitting. When decisions about alcohol use proceed one drink at a time, a perception of zero risk in a single drink may contribute to heavy drinking.