Abstract: Spatial patterns and temporal dynamics of animal populations are fundamental for understanding species distribution and informing conservation management, particularly for transboundary species. The China~Laos border represents a key transboundary range for Asian elephants. This study compiled distribution records of Asian elephants in the border region of Mengla county, Yunnan province, from the 1970s to 2025, and applied a 5 km × 5 km grid-based presence/absence approach to analyze their spatiotemporal dynamics under a unified spatial scale. Results show that the overall distribution pattern shifted from fragmented and localized to increasingly continuous and expanding. (1) The Shangyong subpopulation remained relatively stable during 1976-2007 (9~20 occupied grids), expanded after 2010, and reached 104 grids by 2025, with multidirectional expansion beyond the reserve. (2) The Mengla subpopulation experienced a trajectory of sporadic occurrence, temporary absence, re-establishment, and rapid expansion. Grid numbers ranged from 6~18 during 2002-2008, increased markedly after 2010 (42 grids in 2012), and peaked at 110 grids in 2022, forming a north~south banded distribution. (3) At the regional scale, the two subpopulations gradually shifted from isolated to connected distributions, with continuous increases in occupied grids during 2006-2018 and a marked rise during 2021-2025, indicating enhanced spatial connectivity. (4) Spatial expansion exhibited strong corridor dependence, primarily along transboundary forest belts and movement pathways, with elephant ranges extending beyond existing protected areas and increasing use of non-protected landscapes. This study reveals the spatiotemporal evolution of Asian elephant distribution in the transboundary region of Mengla County, providing a spatial basis for joint monitoring and conservation management of transboundary elephant populations.