The A -site spinel compound Mn Sc2 S4 exhibits strong frustration effects with a low ordering temperature (TN =2.3 K). Detailed neutron-scattering investigations have been performed to study the magnetic ordering process and the associated magnetic excitations. The magnetic structure found at T=1.5 K is a spiral within the a-b plane characterized by a propagation vector of q= (3 4,3 4,0). The magnetic ordering process is spectroscopically reflected by a change from a purely quasielastic to an inelastic response. The quasielastic line width corresponds to a magnetic energy scale of ≈1 meV which is consistent with the spin wave stiffness as determined from the magnon dispersion at low temperatures.