The present invention relates to a hopper for preventing theft of undispensed products from a vending machine. The disclosed anti-theft hopper receives dispensed products and allows customers to retrieve dispensed products, but prevents unauthorized access to the interior of a vending machine through the product delivery port. The anti-theft hopper has a first opening through which dispensed products enter the hopper and a second opening through which dispensed products are retrieved by customers. A hopper flap is pivotally coupled to the hopper, wherein the hopper flap is adaptable to pivotally swing over products dispensed into the hopper to allow consumers to retrieve dispensed products from the hopper and wherein the hopper flap is further adaptable to prevent unauthorized access to undispensed products by blocking the insertion of a protruding device through the hopper.