The coupled interfacial Mn and Ru spin configurations in a SrRuO3(SRO)/SrMnO3(SMO) superlattice are investigated with x-ray resonant techniques. With an out-of-plane applied field H, a net Mn moment is induced opposite to (along) H below (above) SRO Curie temperature TC, due to changes in interfacial antiferromagnetic Ru–Mn coupling. In comparison with the Mn moment induced along an out-of-plane field below TC, the Mn moment induced along an in-plane field is five (three) times smaller below (above) TC, due to frustration in the Ru–Mn coupling. Despite its in-plane anisotropy, the G-type antiferromagnetic SMO favors out-of-plane over in-plane canting of Mn moments.