This study investigates the solo diner’s unplanned discretionary buying and dedicational behaviour intentions. More specifically, by applying Cognitive Appraisal Theory (CAT), the study aims to understand the relationship among solo diners’ perception of interaction with restaurant employees and nonverbal communication with peer diners, emotional responses, and behavioural intentions in a full-service restaurant. The study findings point to the significant impact of nonverbal customer-to-customer (C2C) and customer-to-employee (C2E) interaction quality on emotions and two kinds of behavioural intentions (i.e., enhancement and advocacy intentions). Negative emotions were found to significantly influence discretionary unplanned buying and enhancement intentions while positive emotions had significant impacts only on advocacy intention. Lastly, the mediating effect of positive and negative emotions between interaction quality and behavioural intention was confirmed. Beyond contributions to the literature, the findings can also help practitioners become more aware, and address the needs, of this lucrative, largely ignored market.