Dengue has rapidly expanded in XXX affecting all 77 districts. It was first reported in 2004 in XXX, a tropical, lowland district. Climate change has resulted in geographic expansion of Dengue with cases reported from higher altitude and mountainous regions. Since COVID-19 pandemic in XXX, sporadic cases of co-infection with Dengue have been reported raising significant public health concern.This study aims to investigate clinical, laboratory and epidemiological features of Dengue-COVID-19 co-infection at tertiary hospital located in temperate climate region in a low- and middle-income country.A cross-sectional study was conducted during July to October 2023 among patients testing positive for Dengue (via NS1 antigen and/ IgM antibody). SARS-CoV-2 reverse-transcriptase polymerase-chain reaction (RT-PCR) was assessed in same cohort who developed symptoms of COVID-19. In-hospital patient records were used for data collection. Patient demographics, clinical features and laboratory findings were analyzed.Total 62 Dengue positive patients were admitted among which SARS-CoV-2 RT-PCR was positive in 33 (53.2%) patients. Mean age was 42.56±17.32 years. There were 54.8% male. Among co-infection cases, majority presented with fever (87.9%), myalgia and joint pain (87.9%), cough (27.3%), headache (90.9%) and gastrointestinal symptoms (45.5%). Laboratory results revealed overlapping markers like thrombocytopenia (90.9%) and leucopenia (51.5%). Co-infection was associated with higher risk of complications, longer hospital stay and death compared to mono-infection.The emergence of Dengue-COVID-19 co-infection in temperate region of XXX reflects the evolving epidemiology of climate-sensitive diseases; as rising temperatures enable Aedes mosquitoes to inhabit higher altitudes likely facilitated by climate change. Our findings support this geographic shift with more than half of Dengue positive patients also testing positive for SARS-CoV-2 indicating simultaneous community transmission. The overlapping clinical and laboratory features in Dengue-COVID-19 co-infection made the diagnosis challenging. These findings highlight the need for strengthened surveillance, improved diagnostic capacity and preparedness for emerging co-infections in regions newly affected by Dengue.This study highlights significant public health threat posed by emergence of Dengue-COVID-19 co-infection in temperate region due to climate change. As Dengue continues to expand to higher altitude, climate-sensitive disease surveillance should be strengthened in these regions.