Objective　To understand the serotypes and sources of dengue virus (DENV) in Yunnan Province in 2023, providing a scientific basis for dengue fever prevention and control. Methods DENV nucleic acid testing and virus isolation were performed on the serum samples of dengue fever cases diagnosed at three national monitoring sites in Yunnan Province (Longchuan County, Menghai County, Hekou County) in 2023. Dengue virus envelope (E) gene sequencing was performed on positive serum samples and dengue virus isolates, and phylogenetic analysis was conducted using molecular biology software. Results A total of 1 006 dengue fever cases were reported at three monitoring sites in 2023, including 838 imported cases, 161 cases imported from other counties and cities in Yunnan, and 7 autochthonous cases. Among 371 serum samples, 351 were found DENV-positive, including 305 DENV-1 positive samples (174 imported from Myanmar, 1 imported from Laos, 1 imported from Vietnam, 99 imported from Jinghong, 26 imported from Ruili, and 4 local cases), 43 DENV-2 positive samples (8 imported from Myanmar, 6 imported from Jinghong, 26 imported from Ruili, and 3 local cases), 1 DENV-3 positive sample (imported from Myanmar), 1 DENV-4 positive sample (introduced from Ruili), and 1 untyped case. A total of 23 DENV strains were isolated, including 9 strains of DENV-1, 12 strains of DENV-2, 1 strain of DENV-3, and 1 strain of DENV-4. All DENV-1 strains from three monitoring sites belong to genotype I but were located on different evolutionary branches. The DENV-2 strains from Menghai County and Longchuan County belonged to the Cosmopolitan genotype and Asian I genotype, respectively. The DENV-3 strain from Longchuan County belonged to genotype I, and the DENV-4 strain from Longchuan County belonged to genotype I. Conclusions During the dengue fever epidemic season, the border regions of Yunnan Province face dual pressures from both international and domestic imported dengue cases. Imported or introduced cases carried DENVs of serotypes 1-4 (with five genotypes in total), leading to local outbreaks caused by these cases. Imported and local DENVs originated from Southeast Asian countries and exhibited distinct geographic distribution characteristics.