Protein fingerprint analysis using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry was investigated for qualitative identification and differentiation of cashmere and yak fibers. Mass spectra of a total of 25 cashmere and 7 yak fibers were obtained and analyzed. Three ion peaks that are specific only to cashmere fiber were identified as m/z 2036, 2634, and 3266. On the other hand, two ion peaks at m/z 2503 and 2519 can be used as fingerprint ions for yak fiber. This test method can be effectively used in differentiating cashmere fiber from yak fibers in the item with a fraudulent label. We hoped that the use of this identification method could reduce the fraudulent labeling problem in the luxury fiber market.