Research and development of marine renewable energy are progressing in the world. To install generating devices in the ocean, the environmental impact assessment is required. In particular, if we install tidal and oceanic current turbines, fish strikes with turbines are concerned by regulators and local fisheries. In addition, other negative impacts such as noise, current change, etc. may occur due to installation of the devices. This paper reviews environmental impact assessments in terms of tidal and oceanic current turbines. In Japan, several projects regarding with tidal and oceanic current power generation have started. Therefore, this paper also intends to introduce the current situation for Japanese regulators and developers.