Since decades, there have been no reports on the fish resource of the Tibet reach of the Lancang River, China. To gain a contemporary understanding of the corresponding fish communities, field surveys on fish resources were conducted in the main stream and major tributaries of the Tibet reach of the Lancang River in April and September 2017, April, July, and October 2018, and April and September 2019. Fish samples were caught using drifting gillnets (mesh size: 2.5 cm and 7.0 cm). A total of 13 fish species from 2 orders and 5 families (subfamilies) were collected with 9 indigenous fish species and 4 exotic fish species. Omnivorous and carnivorous fishes accounted for 92.3% and 7.7% of total fish, respectively. Benthic and slow-flowing fishes accounted for 61.5% of the fish species. Schizothorax lissolabiatus, S. lantsangensis, Ptychobarbus kaznakovi, and Schizopygopsis anteroventris were the dominant species. The Shannon-Wiener index, Pielou evenness index, and Margalef richness index of the fish community were 0.570–1.249, 0.585–0.901, and 0.504–1.423, respectively. In general, the fish community structure of the Tibet reach of the Lancang River was simple and stable. All historically recorded indigenous fishes were sampled, while all exotic fishes were recorded for the first time. To protect the indigenous fish resources in the Tibet reach of the Lancang River, it is suggested to strengthen the habitat protection, artificial domestication, and breeding of indigenous fishes, as well as to focus on the control of exotic fish populations and prevent invasion.