According to the 2011 Census of India, the town of Longleng had a population of 7,613, though this number has grown steadily in the subsequent decade. The broader Longleng district has a population of over 50,000.
The demographic composition is almost entirely indigenous, with the Phom Naga tribe constituting the vast majority of the population. A small percentage of residents belong to other Naga tribes or are non-tribal migrant workers from mainland India engaged in government service, trade, and construction.
Christianity is the predominant religion, with the majority of the population belonging to the Baptist denomination. The literacy rate in Longleng town is notably high, standing at over 80%, a reflection of the emphasis placed on education by both the community and local church organizations. English is the official medium of education, while Phom is spoken at home, and Nagamese serves as the primary lingua franca for inter-tribe communication.