Effects of Fe-substitution on the crystal structure and magnetic correlations of the geometrically fruStrated anti ferromagnets YBaCo_4-xFe_xO_7+δ(x=0,0.2,0.4,0.5,0.6, and 0.8) have been studied by neutron diffraction, Mössbauer spectroscopy, and acsusceptibility. The compounds YBaCo_4-xFe_xO_7+δ have a special layered-type crystal structure with an alternating Kagomé(6csite) and triangular(2a site) layers along the c axis. Fe³⁺ ions are found to be substituted at both the crystallographic 2a And 6 c sites of Co ions. Mössbauer results show a high spin state of Fe³⁺ ions in atetra hedral coordination. A reduction in the distortion of the Kagomé lattice has been observed with the Fe-substitution. The correlation length of the short-range antiferromagnetic ordering decreases with the Fe-substitution. The sharpness of the magnetic transition also decreases with the Fe-substitution.