Hybrid materials provide an efficient alternative route on improving the thermoelectric performance compared with doping elements. Especially, the insertion of carbon nanotubes plays an effective role in modulating the electrical transport properties and phonon scattering simultaneously. We fabricated a multi-walled carbon nanotube (MWCNTs) doped α-MgAgSb-based hybrid material and researched its thermoelectric properties in detail. The introduced MWCNTs enhanced carrier transport due to the metallic character of MWCNTs and phonon dispersion by the additional interfaces of insertions. The results showed that the electrical conductivity in α-MgAgSb/CNTs was remarkably enhanced especially at MgAg0.97Sb0.99/0.15 wt. % CNTs boosting to 1.6 times than that of CNTs-free MgAg0.97Sb0.99. In addition, the thermal conductivity(κ0.1) of MgAg0.97Sb0.99/0.1 wt. % CNTs was reduced to 0.85 κ0. As a result, the ZT value at room temperature was efficiently improved from 0.55 to 0.83, 1.5 times higher, and a high ZT value of 1.05 at 375 K was obtained. In addition, the dimensionless material factor B* increased from 0.98 to 1.49 at the doping level of 0.1 wt. % CNTs at 300 K, which revealed that MWCNTs significantly enhanced the thermoelectric performance of α-MgAgSb.