During the past 50 years, there has been a growing awareness of environmental issues related to energy technologies and natural resource utilization. A growing global population demands augmenting amounts of energy and goods without big discovery of conventional resources (apart from Zohr and Glafkos offshore fields in Mediterranean Sea, Egypt, and Republic of Cyprus, respectively); leading companies and countries turn their interest in unconventional resources such as shale oil, shale gas, and gas hydrates. Although gas hydrates are assumed part of the alternative energy sources of the future, they exhibit possible environmental risks for both the marine ecosystem and atmosphere environment. This chapter presents the fickleness of methane hydrate (MH) that either takes place naturally or is triggered by anthropogenic activities. Furthermore, it explains the climate change (methane discharged to the atmosphere has 21 times more global warming contingent than carbon dioxide) and the sea acidification (more than half of the dissolved methane retains inside seafloor by microbial anaerobic oxidation of methane) caused by methane hydrate release. Moreover, it presents the seafloor instability when methane hydrated block sediments due to augmentation of temperature or pressure difference. Finally yet importantly, environmental risks and hazards during the operation of production and drilling hydrate reservoirs occupy a significant position in the presentation of this research.