E-commerce has fundamentally transformed the landscape of retail, enabling consumers to buy and sell products online without the constraints of traditional brick-and-mortar stores. This shift is largely attributed to significant advancements in technology, which have facilitated seamless transactions through various digital platforms. The first issue to be discussed is in terms of regulatory approaches to predatory pricing, Indonesia’s Anti-Monopoly Law requires numerous elements to be fulfilled before initiating investigations, leading to a lengthy process overseen by the Komisi Pengawas Persaingan Usaha (KPPU). In contrast, the United States employs a more streamlined approach under the Sherman Act and the Clayton Antitrust Act, requiring fewer elements to establish a prima facie case, thus facilitating quicker assessments and enforcement actions. Secondly, emerging predatory pricing concerns can be caused by product prices that are set too low. In events such as flash sale and Black Friday, those are created as part of the business’ marketing strategy to create more profit as well as gain traction with their consumers. A comparative analysis between how Antitrust Law in Indonesia governs predatory pricing cases and how Antitrust Act in the United States of America governs their will reveal how efficiency and effectiveness is substantiation in order to supervise business practices. This thesis utilizes a normative empirical research method that will shed light on the operational dynamics of e-commerce but also emphasizes the need for robust regulations that safeguard both consumers and businesses from exploitative practices. Additionally, this comparative analysis highlights the efficiency versus complexity of both systems, revealing how each country addresses emerging predatory pricing concerns—especially during promotional events like flash sales and Black Fridays. The United States’ implementation of its Antitrust Act has shined a light on how efficiency could be improved on how KPPU handles their cases. Furthermore, flash sale and Black Friday that are held in e-commerce platforms and/or online shops may show signs of selling at a loss or below cost but that does not mean that the business has a negative or malicious intent to injure or remove competition through predatory pricing or other means. Understanding these nuances is essential for developing fair regulatory frameworks that balance competitive practices in the rapidly evolving e-commerce sector.