Dengue is a public health issue in tropical south-eastern Asia responsible for significant morbidity and mortality. Informationon dengue epidemiology is necessary for developing strategies to control infections effectively. In the Lao People’s DemocraticRepublic (Lao PDR), Champasak and Savannakhet provinces account for around 30% of the national dengue burden. Inthis study, the dengue epidemiological profile in these two southern provinces of Lao PDR was described by analysingseasonal and spatial dengue notification data from 2003–2020 using the long-term mean (LTM) method. Savannakhet hada higher LTM (132.0 cases/month, 95% confidence interval [Cl]: 92.2–171.7) than Champasak (113.3 cases/month, 95%CI: 86.0–140.5), with peaks in dengue notifications following the rainy season in both provinces. The highest notificationrates were observed in July to September; these months were also when the LTM was most frequently exceeded. Previously,dengue notifications were largely confined to the western districts of Savannakhet and the northern districts of Champasak,but more recently, notifications have increased in the eastern districts of Savannakhet and southern districts of Champasak.While the notification rate remained high in children and young adults (5–30 years), especially among students and farmers,a shift in the age structure of dengue cases was observed, with a greater proportion of notifications now occurring in thoseaged over 30 years. Community-based vector control and prevention programmes are needed to restrict the spread of dengueinto new geographical areas in the southern provinces of Lao PDR.