Spin thermoelectric effects in BN-embedded zigzag graphene nanoribbons (ZGNRs) are studied by a first-principles method. The multiple spin-up (spin-down) quasi-bound states below (above) the Fermi level can be introduced by the BN bonded pairs, leading to the dip structures in the transmission spectra. We further find that the spin thermoelectric effect at the Fermi level is obviously stronger than the corresponding charge thermoelectric effect. As the more BN bonded pairs are gradually doped from the edge to middle regions, the spin thermoelectric figure of merit (FOM) can be improved up to ten times than the charge thermoelectric FOM. A pure spin current can also be achieved in the BN-embedded ZGNRs under an external thermal bias. (C) 2015 Published by Elsevier B.V.