Abstract: Objective In the past 40 years, there have been almost no reports on investigations and research of fish resources in the Zhangjiang River. It is necessary to investigate and understand the current status of fish resources in the Zhangjiang River. Methods In March and October 2023, the fish resource survey was conducted using gill nets and cage nets to analyze fish diversity, dominant species, and the invasive status of alien fish. Results A total of 28 species of fish were collected in the survey, including 22 species of native fish and 6 species of alien fish. Alien fish accounted for 21.43% of the total number of species, 80.67% of the total quantity, and 65.22% of the total weight. The dominant species were Coptodon zillii, Sarotherodon galilaeus, Oreochromis niloticus, Parachromis managuensis, and Hypophthalmichthys molitrix. The Shannon-Wiener indices for March and October were 1.841 and 1.997, the Pielou indices were 0.636 and 0.656, and the Margalef indices were 3.230 and 3.542, respectively. Conclusion Alien fish have become the main group of fish, and Cichlidae fish are the main component of alien fish. The proliferation of alien fish in the Zhangjiang River has led to changes in the community structure of fish. The results of the study could provide scientific references for stock enhancement of fish, protection of native fish germplasm resources, and prevention and control of invasive alien fish.