With high carrier mobility and intrinsic low lattice thermal conductivity, Ag₂Se compounds have attracted increasing attention for thermoelectric application near room temperature. Due to its phase transition at ∼406 K and resulting thermal volume expansion, the growth and thermoelectric properties of large-sized Ag₂Se single crystals have seldom been reported so far. In this work, the vertical Bridgeman method was used for growing bulk Ag₂Se single crystal, with an orientation preference along low-symmetric (201) plane. The Hall mobility as high as 2 000 cm²/(V·s) and weak electron-phonon coupling contributes to a high electronic quality B_E of ∼7.0 in near-room-temperature β-Ag₂Se single crystals, which is superior to the high-temperature phase α-Ag₂Se. The observed low lattice thermal conductivity of 0.8 W/(m·K) at 300 K is due to the low group speeds and strong anharmonicity. A promising peak zT of 0.66 at 375 K and an average zT of 0.65 at 300–375 K were realized in β-Ag₂Se crystals. The low Vickers hardness and good ductile properties were confirmed by experiment and theoretical analysis. This work not only synthesized large-sized and highly-orientated Ag₂Se crystals, but also revealed its great potential of thermoelectric performance and mechanical properties for various applications near room temperature.