PurposeUnethically behaving customers deviating from morally acceptable norms have posed an additional challenge to retailers, frontline employees (FLEs) and other customers in recent crisis-dominant environments. While research concerning customer behaviour ethicality focusses on purchasing modes and consumption behaviour, unethicality in all its facets receives limited attention, leaving dimensions of unethical customer behaviour (UCB) and effective managerial strategies unexplored. The purpose of this paper is to describe dimensions of UCB, investigate its causes, explore its consequences for customers and FLEs and infer practical implications for retail management by collecting customers' and FLEs' views in collaboration of each other.Design/methodology/approachDue to the explorative nature of this research, qualitative semi-structured interviews with 45 customers and 51 FLEs were conducted, following a content analytical approach and the establishment of inter-rater reliability coefficients.FindingsThe findings reveal multiple UCB dimensions operating on situational and individual behavioural levels, targeting mainly employees, followed by customers. The reasons for UCB arising correspond to customers' attitudes, social influences and egoistic motives. UCB imposes risks of financial losses for retailers, due to the wasting of resources as a consequence of employees' stress and emotional exhaustion, demanding managerial boundary-spanning activities. Further, it negatively impacts customers' shopping behaviours, provoking online shopping and shopping avoidance.Originality/valueThe study fills the research gap regarding perceived unethicality of customer behaviour by describing and explaining differing forms of UCB, considering customers' and FLEs' views in retail stores. It develops a UCB framework, identifies UCB dimensions beyond current academic research and derives specific practical implications to make the phenomenon manageable for retailers. The originality of this paper lies in the synthesis of the three UCB dimensions, consisting of antecedents, forms of UCB and consequences for customers and FLEs.