Mhadei Wildlife Sanctuary is located in Sattari Taluka close to Valpoi town. It covers an area of 208 km². This sanctuary covers much of the north-eastern portions of Goa and is connected to the Netravali Wildlife Sanctuary. It is enriched with a high level of biodiversity. Due to the presence of Bengal Tigers in the sanctuary, it is on its way to be declared a tiger reserve, under the Project Tiger.

Mhadei Wildlife Sanctuary consists of innumerable animals comprising mammals, reptiles, amphibians, butterflies, birds and more. Ruddy Mongoose, Indian Gaur, Sambhar Deer, Leopard, Small Indian Civet, Sloth Bear, Black Panther, Barking Deer, Asian Palm Civet, Jungle Cat, Dhole, Slender Lorris, Giant Squirrel, Wild Boar, Mouse Deer, Flying Squirrel, Indian Hare and Bonnet Macaque are the mammals noticed in this area.

The sanctuary is rich in birds and is considered an International Bird Area which protects globally threatened species, Biome-restricted species and also restricted-range species of birds. The various birds which are present in the sanctuary consists of Crimson-backed Sunbird, Nilgiri Wood-Pigeon, White-bellied Blue-Flycatcher, Grey-headed Bulbul, Rufous Babbler, Malabar Grey Hornbill and Malabar Parakeet. As many as 255 species of birds are existent here.

All the large four most poisonous snakes in the country find refuge in the Mhadei Wildlife Sanctuary including the Russell`s Viper, Indian Krait, Spectacled Cobra and Saw-scaled Viper. The sanctuary also possesses several other kinds of snakes like Sri Lankan Cat Snake, Brahminy Blind Snake, Indian Rat Snake, Hump-Nosed Pit Viper, Common Sand Boa, Indian Rock Python, Common Wolf Snake, Tree Snake, Striped Keelback, Copper-headed Trinket Snake, Collared Cat Snake, Banded Racer, Common Bronzeback, Streaked Kukri Snake, Yellow-spotted Wolf Snake, Monocled Cobra, Travancore Wolf Snake, Ocellated Shield Tail, Green Pit Viper, Checkered Keelback, Black Slender Coral Snake, Common Indian Cat Snake, Common Vine Snake, Malabar Pit Viper and others.

Malabar Gliding Frog, Beddome`s Leaping Frog, Endangered Marbled Ramanella, Maharashtra Bush Frog, Mhadei Caecilian, Goa Caecelian, Nadkarni`s Caecilian are some of the amphibians observed here. About 257 species of butterflies are present here including Blue Tiger Butterfly, Common Indian Crow, Southern Birdwing, Common Jezebel, Blue Mormon Stripped Tiger, etc.