Ethnic fermented products are traditional foods which are indigenous to people of different ethnic tribes and are prepared using knowledge passed down from their ancestors. There are uncountable varieties of ethnic fermented food products across the world each with its own distinct substrates and preparation processes. Fermentation is the oldest and most economical way to produce and preserve traditional foods. Microorganisms involved during the fermentation enhance the nutritional value and therapeutic properties of foods with unique flavors, textures, and appearances. Ethnic groups across the world prepare distinctive fermented foods from different vegetable leaves, such as mustard greens, radish leaves, cauliflower leaves, spinach, hangam, colocasia, and turnip. Gundruk in India, Nepal, and Bhutan; Anishi, Hungrii, Ziang-sang, Goyang, and Ankamthu in Northeast India; Sayur asin in Indonesia; Pak-gard dong and Pak-sian-dong in Thailand; and Sunki and Tsuda-Turnip Pickle in Japan, are some such popular flavorful ethnic dishes. This chapter is intended to explore the indigenous knowledge behind the production of leafy vegetable-based fermented foods, along with insights into their nutritional and health beneficial properties. This chapter also emphasizes on techniques to improve quality and thus shelf-life which would aid in the commercialization of these products.