Doping, as a central strategy to control over free carrier type and concentration in semiconductor materials, suffers from the low efficiency at nanoscale. Especially in systems with high permittivity and large Bohr radii such as lead chalcogenide nanostructures, the doping efficiency is extremely low (~1%). One of the possible cause is the significant dielectric constant (ε) mismatch between the nanostructure and its surrounding media. We study the dielectric confinement effect on the doping efficiency of Pb, In and Se in lead chalcogenide nanostructures, utilizing the platform of PbSe nanowire field effect transistors (FETs). By increasing the \epsilon of the surrounding medium, the free carrier concentration and the calculated doping efficiency for n-type (Pb/In) and p-type (Se) dopants increases with a given number of dopants. Ultimately, the doping efficiency can be enhanced by >10 fold with barely any dielectric confinement. Mathematically, a modified Delerue’s equation is applied to describe the doping efficiency in PbSe NWs with different dielectric environment, which agrees with our experimental data both from NW arrays and single NW devices. Through single NW FET’s temperature dependent characteristics, we further extract ionization energy of Pb in PbSe NW, consistent with the theoretical calculation.