The purpose of this study is to investigate the association of unplanned buying with post-purchase regret, moderated by consumer-family income and gender, as well as the association of both sales promotion and bankcard payment with unplanned buying in the Saudi market. Drawing on unplanned buying and post-purchase literature, the study tested a model of post-purchase regret. A survey was conducted among Saudi consumers of retail stores in Riyadh, Saudi Arabia. A convenience sample of 927 respondents was taken for data collection, among them 903 were finalized for analysis. The study concluded that there is a positive relationship between unplanned buying and post-purchase regret. An increased association of unplanned buying with post-purchase regret has been found among low-income earners and male consumers. Furthermore, bank-card payment, but not sales promotion, has a significant association with unplanned buying. Practically, consumers and marketers can benefit from the results and recommendations of this study, both avoiding the bad consequences of post-purchase regret. Self-awareness of the factors that cause regret may turn consumers to be more rational in their future buying decisions. Marketers' perceptions of those factors may also be helpful in setting marketing strategies towards their target markets; satisfying, and retaining consumers. The original contribution of this study comes from a lack of research in the Middle East on unplanned buying, post-purchase regret and their relationship antecedents.