Exploring N-type High-entropy materials with both high thermoelectric and mechanical properties is highly desirable for all-high-entropy thermoelectric generators (TEGs) since the thermoelectric and mechanical properties of N-type one are largely behind its P-type counterparts. Herein, a new rock-salt structure N-type high entropy thermoelectric AgBiPbSe2S is introduced with a bandgap of ≈0.43 eV. The atomic radii difference of each component results in a large lattice distortion of 0.246, leading to a low thermal conductivity of 0.36 W m−1 K−1 at 823 K. The figure of merit (ZT) reaches 0.6 for AgBiPbSe2S at 823 K. Moreover, Ag2Se precipitates are included in AgBiPbSe2S to filter low energy carriers for high Seebeck coefficients and to scatter phonons with nanoscale wavelength for ultralow lattice thermal conductivities. Consequently, a peak ZT of ≈1.18 at 823 K and an average ZT of 0.60 at 400–823 K are obtained for Ag1.02BiPbSe2S. More importantly, high mechanical properties are also obtained in Ag1.02BiPbSe2S, of which the Vickers hardness and flexural strength are ≈209 Hv and 32 MPa, respectively, originating from the enhanced lattice friction by chemical short-range disorder (i.e., high entropy effect) and dispersion strengthening caused by Ag2Se nanoprecipitates.