Binge drinking is common among young adults, putting them at increased risk for severe alcohol related health outcomes and mortality. Past research links subjective responses to alcohol (i.e., how individuals experience its rewarding or impairing effects) to risk for future negative alcohol related health outcomes. Further work demonstrates that context (e.g. drinking in the presence of others or in certain locations such as bars and restaurants) may increase the rewarding effects of alcohol and drive heavy binge drinking behavior. However, most research on drinking context, subjective responses to alcohol, and drinking behavior has been conducted in the laboratory or using retrospective measures, which limits ecological validity. High resolution ecological momentary assessment (HR-EMA) provides a promising solution to these limitations. HR-EMA allows researchers to measure drinking behavior and related outcomes (e.g., drinking context, alcohol subjective responses) in real time in a naturalistic setting. The present study used HR-EMA to evaluate subjective responses to alcohol in different contexts along two domains: in the presence or absence of others and in different physical locations. Participants were 21-29 year old regular heavy binge drinkers, who completed smartphone-based EMA sessions where they recorded the quantity and type of alcohol they consumed, as well as their context and subjective responses to alcohol. Generalized estimating equations (GEE) analysis revealed significantly higher standard drinks consumed and eBAC levels for participants who drank with others as opposed to alone and those who drank in bars and restaurants compared to other locations. In addition, participants reported greater reward (stimulation and wanting more alcohol) when drinking with others compared to alone and when drinking at bars and restaurants compared to other locations. Significant interactions between time and context indicate that differences in subjective responses associated with reward are especially significant later in naturalistic drinking episodes. Conclusions: Drinking in the presence of others and at certain locations associated with alcohol (e.g., bars and restaurants) increase both consumption and rewarding responses to alcohol among young adult heavy binge drinkers and present as a significant risk factor for increased alcohol use.