Based on the 2007 national census conducted by the Central Statistical Agency of Ethiopia (CSA), this town had a total population of 46,139, of whom 23,000 were male and 23,139 female. The majority of the inhabitants practiced Ethiopian Orthodox Christianity, with 80.49% reporting that as their religion, while 18.46% of the population said they were Muslim.

The 1994 national census reported a total population for Weldiya of 24,533 in 5,413 households, of whom 11,689 were male and 12,844 were female. The two largest ethnic groups reported in this were the Amhara (93.92%), and the Tigrayan (4.32%); all other ethnic groups made up 1.76% of the population. Amharic was spoken as a first language by 95.2%, and 3.75% spoke Tigrinya; the remaining 1.05% spoke all other primary languages reported. 79.75% of the population practiced Ethiopian Orthodox Christianity, and 19.44% of the population said they were Muslim.