Diwali is a colorful traditional festival in India. But the festival is observed in many other countries of South and Southeast Asia and others like Malaysia, Myanmar, Nepal, Singapore, Sri Lanka, Thailand, etc. The main day is observed as a National Holiday in many countries. It is the harvest festival symbolizing the spiritual victory of light over darkness. It signifies the prosperity and fertility of the community. Diwali illuminates the countries with joy and dazzles the houses with light, foods, decoration, new dresses, and smile in their faces. It is an exquisite Intangible Cultural Heritage of entire South and Southeast Asia. This article will discuss the uniformity and heterogeneity of Diwali Festival in these South and Southeast Asian countries.