Denasalization is a widely detected but not well documented and thus poorly understood phonetic or phonological process in Chinese dialects. The plain nasal consonants in Middle Chinese may remain as plain nasals such as in Wu dialects, have conditionally changed into plain fricatives or approximants such as in Mandarin dialects, or become post-oralized. This paper discusses acoustic and aerodynamic data of the post-oralized nasal consonants from four major Chinese dialect groups—Shanxi Jin dialects, Cantonese dialects around the Zhongshan area, southern Min dialects (Xiamen and Chao-Shan areas), and the Qingxin Hakka. The presented phonetic data reveal details of the denasalization process in Chinese dialects in particular and shed light on the understanding of historical sound change in general.