Transparent conducting oxides are increasingly important for optoelectronic and thin film transistor applications. La doped BaSnO₃ is a strong candidate for its high transparency, high carrier concentration, high mobility and abundancy. However, due to the lack of lattice-matched substrates, the mobility of La:BaSnO₃ remains inferior to single crystals. Here, by constructing a novel approach via delta doping La:BaSnO₃ in a BaSnO₃/La:BaSnO₃/BaSnO₃ (BSO/LBSO/BSO) heterostructure, we achieved room temperature mobility enhancement up to 110 cm²⸱V⁻¹⸱s⁻¹ while keeping the high carrier concentration at 5 × 10²⁰ cm⁻³, reaching to the highest electrical conductivity in BaSnO₃ based systems. The mobility is enhanced more than 100% compared to our La:BaSnO₃ films, which is among the highest mobility in BaSnO₃ based films and heterostructures. From atomic structural investigations, we found that both (1) the carrier confinement due to delta doping and (2) dislocation-free La:BaSnO₃ conducting channel, revealed by atomic resolution scanning transmission electron microscopy (STEM) studies, are responsible for mobility enhancement. The enhanced mobility from heterostructure approach is widely applicable for transparent electrodes and high current thin film transistor applications.