Mobile warehouses have emerged as a promising concept for improving the efficiency of last-mile distribution in urban areas, yet their transport-system implications remain insufficiently understood. Limited evidence exists on how vehicle choice influences mobile warehouse location decisions and downstream transport efficiency. This study assesses the impact of vehicle type on mobile warehouse–based last-mile distribution using an empirical urban case study. We combine GPS-based delivery demand data with location optimization models (k-center and p-median) to evaluate multiple vehicle regimes, including conventional vans, electric vehicles, and cargo bikes. Transport efficiency is assessed using vehicle kilometers traveled per delivery and travel time per delivery. The results indicate that mobile warehouse locations are largely insensitive to vehicle type, while transport efficiency outcomes are strongly influenced by demand density and vehicle characteristics. In dense demand settings, mobile warehouse solutions combined with smaller or medium sized electric vehicles reduce vehicle kilometers traveled per delivery, whereas benefits diminish in low-demand-density scenarios. The findings suggest that mobile warehouses can contribute to efficient and potentially more sustainable urban freight systems under specific contextual conditions. Rather than vehicle choice being the primary driver, transport efficiency is largely shaped by demand structure and spatial distribution, particularly when mobile warehouses are deployed. The study provides practical insights for urban freight planners by identifying the spatial and operational conditions under which mobile warehouse-based distribution generates measurable transport efficiency gains.