From May 2022 to April 2023, dengue virus serotype 3 (DENV-3) was identified in 601 travel-associated and 61 locally acquired cases in Florida, USA. All 203 sequenced genomes belonged to the same genotype III lineage, indicating potential transmission chains with limited sustained local transmission. DENV is not endemic in the continental US, with most cases among travelers. In Florida, DENV infections are primarily reported among travelers, though local outbreaks have occurred in the past. In early 2022, an increase in travel-associated DENV infections was noted, primarily among travelers returning from Cuba. A DENV-3 outbreak was reported in Cuba in July 2022, and DENV-3 case increases were also documented in other countries in the Americas. In July 2022, Miami-Dade County issued a mosquito-borne illness advisory after the first locally acquired DENV infection in 2022 was confirmed in a Florida resident. During the study period, 1,037 DENV infections were reported, with 966 (93%) being travel-associated and 71 (7%) locally acquired. DENV-3 was the most frequently identified serotype. Among DENV-3 cases, 601 (91%) were travel-associated and 61 (9%) were locally acquired. Most DENV-3 case-patients were White or Hispanic or Latino. Most travel-associated DENV-3 cases were from Cuba, with Miami-Dade County having the most cases. Locally acquired cases were mostly in Miami-Dade County. Genomic analysis revealed that all DENV-3 cases belonged to genotype III and clustered within the novel American II lineage. The phylogenetic tree showed low genomic diversity and frequent movement of DENV between Cuba and Florida without establishing sustained local transmission. The study used epidemiologic surveillance and genomic sequencing to identify a newly emerging lineage of DENV-3 genotype III that caused an unusually large number of travel-associated and locally acquired DENV infections in Florida, particularly in Miami-Dade County. The analysis suggests that locally acquired cases were driven by a large number of case-patients with recent travel to Cuba, and that DENV persistence in Florida was limited. Close monitoring of DENV activity internationally and increasing healthcare provider awareness about DENV identification and testing can strengthen preparedness and response to future introductions in non-DENV-endemic areas.From May 2022 to April 2023, dengue virus serotype 3 (DENV-3) was identified in 601 travel-associated and 61 locally acquired cases in Florida, USA. All 203 sequenced genomes belonged to the same genotype III lineage, indicating potential transmission chains with limited sustained local transmission. DENV is not endemic in the continental US, with most cases among travelers. In Florida, DENV infections are primarily reported among travelers, though local outbreaks have occurred in the past. In early 2022, an increase in travel-associated DENV infections was noted, primarily among travelers returning from Cuba. A DENV-3 outbreak was reported in Cuba in July 2022, and DENV-3 case increases were also documented in other countries in the Americas. In July 2022, Miami-Dade County issued a mosquito-borne illness advisory after the first locally acquired DENV infection in 2022 was confirmed in a Florida resident. During the study period, 1,037 DENV infections were reported, with 966 (93%) being travel-associated and 71 (7%) locally acquired. DENV-3 was the most frequently identified serotype. Among DENV-3 cases, 601 (91%) were travel-associated and 61 (9%) were locally acquired. Most DENV-3 case-patients were White or Hispanic or Latino. Most travel-associated DENV-3 cases were from Cuba, with Miami-Dade County having the most cases. Locally acquired cases were mostly in Miami-Dade County. Genomic analysis revealed that all DENV-3 cases belonged to genotype III and clustered within the novel American II lineage. The phylogenetic tree showed low genomic diversity and frequent movement of DENV between Cuba and Florida without establishing sustained local transmission. The study used epidemiologic surveillance and genomic sequencing to identify a newly emerging lineage of DENV-3 genotype III that caused an unusually large number of travel-associated and locally acquired DENV infections in Florida, particularly in Miami-Dade County. The analysis suggests that locally acquired cases were driven by a large number of case-patients with recent travel to Cuba, and that DENV persistence in Florida was limited. Close monitoring of DENV activity internationally and increasing healthcare provider awareness about DENV identification and testing can strengthen preparedness and response to future introductions in non-DENV-endemic areas.