In Amazon's marketplaces across the globe, multiple sellers sell the same product, leading Amazon to introduce BuyBox. This box‐like feature, located on the top‐right corner of product pages, prominently displays a single seller at a given time. Using a choice model and a panel dataset of over 290,000 unique grocery products from five countries, our study investigates the key factors that influence BuyBox assignments. We found that winning the BuyBox is primarily determined by competitive pricing—being the lowest‐price seller for a 180‐day period significantly improves the chances of a BuyBox assignment. Furthermore, maintaining low current product prices, low sales ranks, and minimal out‐of‐stock percentages are crucial in becoming a BuyBox seller. These findings affect Amazon and its extensive network of over 2 million third‐party sellers, who navigate the increasingly competitive and dynamic E‐commerce landscape.