As an abundant, clean, and predictable source of renewable energy, tidal current energy provides a cost-effective alternative to fossil fuels. Tidal current energy harvesting technologies are still at their early stages of development. Even some advanced demonstration projects with full-scale tidal current energy converters (TCECs) still face considerable technical barriers, and their environmental impacts are unclear. This study presents a comprehensive overview of the state-of-the-art of tidal current energy harvesting schemes and life cycle assessment (LCA) studies of TCECs. By reviewing the state-of-the-art of research and development efforts of tidal current energy harvesting technologies, key advancements required for their successful commercialization at the utility scale in the tidal current energy industry are identified. Detailed LCA studies of TCECs are presented to indicate their energy consumption and environmental impacts. Additionally, some comprehensive comments of development of TCECs and LCA are presented, which can be used to guide decision making towards more sustainable energy practices.