  We derive a master equation that allows us to study non-equilibrium dynamics
of a quantum antiferromagnet. By resorting to spin-wave theory, we obtain a
closed analytic form for the magnon decay rates. These turn out to be closely
related to form factors, which are experimentally accessible by means of
neutron and Raman scattering. Furthermore, we compute the time evolution of the
staggered magnetization showing that, for moderate temperatures, the magnetic
order is not spoiled even if the coupling is fully isotropic.
