The majority of Sikkim's residents today are of Nepali ethnic-national origin who came to the province in the 19th century. The native Sikkimese, consist of the Bhutias, who migrated from the Kham district of Tibet in the 14th Century, and the Lepchas who are believed to have migrated from the far east. Tibetans reside mostly in the northern and eastern reaches of the state. Immigrant resident communities not native to the state include the Marwaris, who own most of the shops in South Sikkim and Gangtok, the Biharis, most of whom are employed in blue collar jobs, and the Bengalis.

Hinduism and Buddhism are the religions professed by most Sikkimese. Sikkim also has a small Christian population, consisting mostly of people of Lepcha origin, converted to the faith after British missionaries started preaching in the region in the late 19th century. The state has never had inter-religious strife. Mosques in downtown Gangtok and Mangan also serve the minuscule Muslim population.

Life in Sikkim is according to some, a never - ending festival, for there are vibrant festivities throughout the year. They are the reflection of the rich cultural heritage of the state, which combines Buddhism and Hinduism, with the original traditions of the Lepchas. The major monasteries like Pemayangtse, Tsuklakhang, Enchey and Rumtek are important venues for Buddhist festivals. Pang Lhabsol, Drukpa Tseshi, Losoong, Saga Dawa and Dasain are the most popular festivals. A favourite form of celebration is drinking of 'Chang', the millet beer of the Himalayas . Packed into tall bamboo containers, the drink is sipped through a bamboo pipe.

Nepali is the lingua franca of Sikkim. English and Hindi are also spoken and understood in most of Sikkim. Other languages spoken in Sikkim include Bhutia, Dzongkha , Groma, Gurung, Lepcha, Limbu, Magar, Majhi, Majhwar, Newari, Rai, Sherpa, Sunuwar, Tamang, Thulung, Tibetan, and Yakha.