The layered A-type antiferromagnet Pr0.5Sr0.5MnO3 has been investigated by neutron scattering. Antiferromagnetic ordering is observed with a T-N of 152.3 K and an exponent beta of 0.148+/-0.01 that suggests 2d Ising behavior. The spin-wave excitations, measured for the neutron momentum transfer q perpendicular to the ferromagnetic planes at 2 K, show a gap of 2.3+/-0.2 meV at the zone center [0.5 0 0.5]. The dispersion near zone center yielded the spin-wave stiffness coefficient D-SW of similar to100+/-10 meV A(2) which is twice the value found in the isostructural A-type antiferromagnet LaMnO3. The double-exchange interaction, introduced by hole doping, enhances D-SW in Pr0.5Sr0.5MnO3. The spin wave dispersion at low q fits the dispersion of the Heisenberg model with nearest neighbor exchange interaction and single ion anisotropy. (C) 2004 American Institute of Physics.