The (In,Mn)AS/InAS p-n heterojunctions were fabricated, and their electronic and magnetic properties were characterized. The magnetic field dependence of the I-V characteristics of the heterojunctions were measured. In a junction consisting of a p-type, two phase ferromagnetic In 0.91Mn 0.09As film and n-type InAs, a shift in the I-V characteristics was observed with an applied magnetic field. The magnetic fields applied perpendicular to the plane of the film led to a decrease in conductance at all temperatures and applied fields. The results show that the magnetoresistive properties of these heterojunctions make them suitable for use in spintronic devices.