(EDTDM)(2)FeBr4 based on pi-d interaction system consists of quasi one-dimensional donor columns and square-lattice magnetic anion sheets (Fe3+ (s=5/2)). It behaves metallic at high temperatures and undergoes a metal-insulator transition at T(MI)similar to15-20K, where the low temperature insulating phase is considered to be magnetic ordered state. The magnetic susceptibility, which is governed by Fe3+ d-spins, obeys the Curie-Weiss law in the high-temperature regime. Below 50K, the susceptibility deviates from the Curie-Weiss law and shows an antiferromagnetic transition at T(N)similar to3K. The anomalous magnetization curves indicate an important role of pi-d interaction in the magnetic behavior.