Thermoelectric materials can convert heat into electricity directly via the Seebeck effect, providing an alternative to global energy demands. Here we present mechanical, dynamical, and thermoelectric properties of YZnAsO, a quaternary oxypnictide, in the framework of Density Functional Theory. The low value of Debye temperature (θD=308.29K) and high value of the Grüneisen parameter (∼1.77) hint for low lattice thermal conductivity (kl), and this is supported by the computed value of ∼0.4 W/mK at 800 K. The electronic transport coefficients are computed using Boltzmann transport equation beyond the constant relaxation time approximation (CRTA) including different scattering mechanisms. While the power factor for hole doping is higher along ‘a’, the kl is extremely low along ‘c’, resulting in a high figure of merit (ZT) along ‘c’. Hence, we predict YZnAsO as a promising n-type oxide thermoelectric owing to its low kl with a high ZT =1.07 at 800 K with 15% maximum thermoelectric efficiency. © 2023 Elsevier B.V.