The Néel temperature of the new frustrated family of SrRE O (RE= rare earth) compounds is yet limited to ~0.9 K, which more or less hampers a complete understanding of the relevant magnetic frustrations and spin interactions and an exploration of potential interesting properties. Here we report on a new frustrated member to the family, SrTb O with a record T = 4.28(2) K, and an experimental study of the magnetic interacting and frustrating mechanisms by polarized and unpolarized neutron scattering. The compound SrTb O displays an incommensurate antiferromagnetic (AFM) order with a transverse wave vector Q = (0.5924(1), 0.0059(1), 0) albeit with partially-ordered moments, 1.92(6) μ at 0.5 K, stemming from only one of the two inequivalent Tb sites mainly by virtue of their different octahedral distortions. The localized moments are confined to the bc plane, 11.9(66)° away from the b axis probably by single-ion anisotropy. We reveal that this AFM order is dominated mainly by dipole-dipole interactions and disclose that the octahedral distortion, nearest-neighbour (NN) ferromagnetic (FM) arrangement, different next NN FM and AFM configurations, and in-plane anisotropic spin correlations are vital to the magnetic structure and associated multiple frustrations. The discovery of the thus far highest AFM transition temperature renders SrTb O a new friendly frustrated platform in the family for studying the nature of magnetic interactions and frustrations and exploring potential macroscopic functionalities and new quantum states.