The district was formed on 26th January 1972 by merging Thodupuzha and Udumbanchola taluks and parts of Kottayam and Ernakulam districts. 

The region also played a significant role in the spice trade during the pre-colonial period. It was a major center for the production and trade of cardamom, pepper, and other spices. The region's strategic location and fertile land made it an important trading center for centuries. 

In the 16th century, the region came under the control of the Portuguese, who established a settlement in Cochin. Later, the Dutch and the British also established their presence in the region. The British took control of the region in the 19th century and established various tea and coffee plantations in the region. 

After India gained independence in 1947, the region became a part of the state of Travancore-Cochin. Later, in 1956, Kerala was formed as a separate state, and Idukki became a part of it. 

Today, Idukki district is known for its scenic beauty, tea and spice plantations, wildlife sanctuaries, and hydroelectric projects. The district has also played a significant role in the social and cultural history of Kerala, with its indigenous tribes, traditional art forms, and festivals.