Magnetic and dielectric properties have been investigated on BiMn2O5 single crystals. Magnetic measurements show that BiMn2O5 becomes antiferromagnetic below TN∼39 K, with short range magnetic correlation existing between TN and T∗∼100 K. Three thermally excited dielectric relaxations at temperatures TN<T<300 K and large intrinsic magnetodielectric effect due to the special arrangement of Mn3+/Mn4+ ions associated with electron hopping between them were observed. The low temperature anisotropic relaxation (TN<T<T∗) along the b-axis, which is insignificant along the c-axis, can be ascribed to electron hopping between the zigzag chains with short range magnetic correlation. The other two dielectric relaxations are also discussed.