This chapter examines oil theft, and other types of transnational organized crime at sea (such as the illicit traffic of narcotics and psychotropic substances standing out), within the framework of maritime security and, particularly, the effective implementation of the International Ship and Port Facility Security Code (ISPS Code). The chapter focuses on Mexico; however, these findings can also apply to other countries facing similar security threats. It also highlights possible solutions associated with the effective implementation of the ISPS Code and other appropriate maritime security measures. An important conclusion is that oil theft and illegal bunkering activities, as well as piratical attacks against offshore platforms, are clearly on the rise in Mexico. It also indicates that there is a new trend in the transportation of drugs and weapons, which involved affixing them in packages to the bulbous bows of vessels, a practice which requires international acknowledgment and appropriate handling measures to effectively tackle this specific unlawful practice. It also includes recommendations concerning the use of remote-controlled underwater vehicles (commonly known as drones) by port authorities for hull inspections. Vast quantities of oil are lost daily in Mexico through theft. Large ocean-going tankers take the majority of the stolen crude oil to selected refineries outside the country. This requires significant efforts and coordination that can only be carried out by well organized criminal rings.