BACKGROUND: Global warming has facilitated the spread of mosquito-borne diseases, including dengue, to non-endemic areas like Italy. People living with HIV (PLWH) are at increased risk of severe dengue, especially during secondary infections, but current vaccination options are constrained by safety considerations. This study assesses the seroprevalence of IgG anti-DENV among PLWH in Italy, after the 2023 Italian autochthonous outbreak. METHODS: This cross-sectional study enrolled PLWH from July to November 2023 in Rome during the abovementioned outbreak. Blood samples were collected and analyzed for IgG anti-DENV using ELISA. Participants were stratified by country of birth and those with immune profiles suitable for live attenuated virus vaccination were identified. Cryopreserved serum samples from 2021 to 2022 were tested to trace the timing of infections. RESULTS: We included 475 PLWH of whom 37 tested positive for IgG anti-DENV, resulting in an overall seroprevalence of 7.79 % (95 % CI 5.54-10.6). The seroprevalence was significantly higher among PLWH born in DENV-endemic countries (37.14 %) compared to Italian (2.86 %). Notably, among the Italian participants, three individuals who had not traveled outside Italy in the past 12 months showed seroconversion during the 2023 outbreak, providing further evidence of autochthonous dengue transmission in the country. This finding underscores the growing relevance of dengue as an emerging public health concern in Italy. Of the 37 seropositive individuals, 34 (91.9 %) had a CD4 count ≥200 cells/μl, indicating that a significant portion of the at-risk population could safely be vaccinated. CONCLUSIONS: Many PLWH have been exposed to DENV, with some experiencing seroconversion during the 2023 outbreak. Most of these individuals could feasibly receive live attenuated virus vaccination without significant risks, but further studies are needed to confirm vaccine safety for PLWH.