Poly(ether ether ketone)/polysulfone blends were obtained by direct injection molding throughout the composition range. The almost full immiscibility and biphasic nature of these blends was seen by differential scanning calorimetry and dynamic-mechanical thermal analysis and their homogeneously dispersed phase by scanning electron microscopy. The elastic modulus showed an usual behavior slightly below additivity. However, the strain-related break properties such as ductility or impact strength showed a surprising and positive, for an immiscible blend, behavior close to additivity both in as-molded and in annealed blends. Some possibilities, such as fast cooling, the largely aromatic nature, similar solubility parameters, different dilatation or Poisson coefficients, and the inherent chemical structure of the blends are discussed as reasons for the observed behavior.