Most dialects of the Chinese language spoken in Yunnan belong to the southwestern subdivision of the Mandarin group, and are therefore very similar to the dialects of neighbouring Sichuan and Guizhou provinces.

Notable features found in many Yunnan dialects include the partial or complete loss of distinction between finals /n/ and /?/, as well as the lack of /y/. In addition to the local dialects, most people also speak Standard Chinese (Putonghua, commonly called "Mandarin"), which is used in the media, by the government, and as the language of instruction in education.

Yunnan's ethnic diversity is reflected in its linguistic diversity. Languages spoken in Yunnan include Tibeto-Burman languages such as Bai, Yi, Tibetan, Hani, Jingpo, Lisu, Lahu, Naxi; Tai languages like Zhuang, Bouyei, Dong, Shui, Tai Lü and Tai Nüa or northern Lao dialect; as well as Hmong–Mien languages.

The Naxi, in particular, use the Dongba script, which is the only pictographic writing system in use in the world today. The Dongba script was mainly used to provide the Dongba priests with instructions on how to carry out their rituals: today the Dongba script features more as a tourist attraction. The most famous Western Dongba scholar was Joseph Rock.