The horned helmet Cassis cornuta, a protected species in some countries, is one of the largest reef gastropods that had been traditionally collected for food and for its shells as ornaments. In the Philippines, this protected species is rarely seen in habitats close to human settlement. However, in a protected area like the Tubbataha Reefs Natural Park (TRNP), C. cornuta are commonly encountered at the vicinity of the Ranger Station. With a dearth of information about this giant reef gastropod, notes on marked-recaptured C. cornuta in TRNP were taken from December 2009 until January 2011; and its trade was noted through surveys of some souvenir shops in Puerto Princesa City. Most of the sampled C. cornuta were large, suggesting the absence of exploitation at the study site. Regression analyses suggest that the shell’s dimensions are significant determinants of body weight. Growth rates declined as shell size increased. Although exploitation of C. cornuta is prohibited under the Philippine law, their shells were openly displayed for sale in a number of souvenir shops in Puerto Princesa City. Given the limited area covered in this study, a nationwide survey is needed to fully document its status in the wild and the extent of its trade. Information on population, growth, survival, other aspects of its biology and its exploitation are needed in proposing a more relevant conservation measure for this vanishing giant reef gastropod.