This study investigates the dynamic interplay between migration, land use changes, and border porosity along the Nigeria–Benin Republic border in Saki West Local Government Area, Oyo State, using geospatial techniques. The research identifies and classifies legal and illegal migration routes, assesses land use/cover changes from 2003 to 2023, and models the region’s border porosity. A 3 km buffer along the border corridor served as the analytical boundary, enabling the digitization of 202 illegal and 4 legal routes through high-resolution satellite imagery and GPS field data. Land use analysis was performed using supervised classification of Landsat imagery, supported by accuracy assessments yielding Kappa coefficients of 0.69 (2003) and 0.65 (2023). The results show a marked decline in cultivated land and a rise in uncultivated, bare earth, and built-up areas, indicating environmental changes linked to migration-driven land transformations. A weighted linear combination (WLC) approach was employed to generate a porosity model integrating natural and human-made factors. Findings reveal moderate porosity driven by extensive unregulated migration routes, minimal infrastructure, and favorable topography. These patterns underscore the challenges of border management and raise environmental sustainability concerns due to agricultural land loss. The study recommends enhanced cross-border cooperation, regular land monitoring, and investment in agricultural diversification to curb illicit trade and foster legal economic activities. By integrating spatial data and modeling techniques, this research offers critical insights into managing border zones where socio-economic, environmental, and security dimensions intersect.