E-commerce has witnessed exponential growth in the past 25 years and in 2015 the ecommerce expenditure was close to $350 billion in the U.S. (Smith & Anderson, 2016), £۵۲٫۲۵ billion in the UK (Moth, 2015). The venues of e-commerce have also diversified including traditional computer-based purchase as well as transactions made on cellphones and using social media links. A recent survey found approximately 80% of Americans have shopped online (Smith & Anderson, 2016) which is a sharp increase from 22% of Americans reported in 2000. In addition, social commerce, such as a purchase made on or through Facebook, is expected to increase as much as $30 billion (Anderson, Brusa, Price, & Sims, 2011). This trend is not unique to America. The advancement of internet and digitization increased the popularity of online shopping around the world including developing countries (Hoang, Chi, Tuan, & Linh, 2016). Though e-commerce advancements are moving at a rapid pace, a comprehensive understanding of consumer behavior lags in online shopping settings. The current paper attempts to investigate consumers’ regret in relation to exerted cognitive effort and justification in online shopping. Justification is an important part of consumer decision making. The rationalization involved in justification can alleviate decision conflict, and can allow people to formulate reasons to justify a difficult decision (Shafir, Simonson, & Tversky, 1993). Thus, justifying a decision is a common practice and consumers are motivated to maximize justification (Bettman, Luce, & Payne, 1998). Justification goal can shape consumers’ decision paths and help them judiciously allocate their finite resources such as cognitive effort or money. Cognitive effort, besides justification, is equally valuable to consumers. Cognitive effort exertion results in increased confidence and accuracy of a decision (Bettman et al., 1998). Though justification and cognitive effort exertion are unique and independent constructs in decision making, cognitive effort can be spent to justify a decision and lower post-decision discomfort. However, this is only probable when the sought information is favorable towards the decision (Liang, 2016). This implies post-decision discomfort may increase when cognitive effort or justification was wasted. The aim of this paper is to explore the function of cognitive effort exertion and justification in relation to regret reduction in the online shopping context. Though it is still cognitively taxing for consumers to conduct systematic product evaluation (Einhorn & Hogarth, 1981), it has never been more convenient to search for and gather information online. Technology provides convenience to consumers but also allows them to gather an abundant amount of product information at their fingertips. In this information age, consumers are surrounded with high quality information (e.g., expert opinions) and have the ability to organize it more efficiently (Goldenberg, Oestreicher-Singer, & Reichman, 2012). Additionally, by using the online decision aids, consumers may be able to reduce the decision cost yet still gain the benefits from cognitive effort expenditure through increased accuracy.