Chronic urticaria is a common condition that can be very disabling when severe. A variety of causes has been reported to induce urticaria, including food, infections, drugs and other factors. In more than 50% of cases of chronic urticaria, however, the cause remains unknown and cannot be ascribed to allergic, physical, environmental or other factors. Although an association between chronic idiopathic urticaria and malignancy has been occasionally reported, such an association remains controversial because it is difficult to demonstrate it is not just coincidental. Here we report the cases of four female patients with occult papillary carcinoma of the thyroid who developed chronic urticaria. In all of these cases, removal of the tumor led to prompt resolution of the urticarial lesions, thus suggesting a pathogenetic relationship between the two. This is the first report of papillary thyroid carcinomas associated with chronic urticaria and highlights how chronic urticaria may be an important cutaneous marker for patients with thyroid carcinoma.