When was India's first devaluation?

First devaluation of the Indian Rupee took place on 19th September, 1949. India devalued the rupee from ₹3.309 to a dollar to ₹4.762. Rupee devalued by 30.5 % as a defensive measure consequent to the devaluation by other ‘sterling area’ countries. You can read about the Balance of Payment Crisis, 1991 – Causes and Measures to Control it in the given link.

The next devaluation of Indian Rupee took place in 1966 and for the third time the Indian rupee devaluation was done in 1991. In 1991, the Indian rupee was devalued in two steps, first on 1st July and again on 3rd July. Devaluation of Indian rupee is done for varied reasons. The imported goods becomes expensive when devaluation is done.

Further readings:

1. Forex Reserves – Meaning, Importance, Advantages (Notes for UPSC IAS exam)
2. New Economic Policy of 1991 – Objectives, Liberalisation, Privatisation, Globalisation