We investigated theoretically electronic and magnetic properties of the perovskite material SrCoO_3−δ with δ ≤ 0.15 using a projector-augmented plane-wave method and a Green's function method. This material is known from various experiments to be ferromagnetic with a Curie temperature of 260 K to 305 K and a magnetic moment of 1.5μ_B to 3.0μ_B. Applying the magnetic force theorem as it is formulated within the Green's function method, we calculated for SrCoO_3−δ the magnetic exchange interactions and estimated the Curie temperature. Including correlation effects by an effective U parameter within the GGA + U approach and verifying this by hybrid functional calculations, we obtained the Curie temperatures in dependence of the oxygen deficiency close to the experimental values.