  We study the emergence of multiband superconductivity with $s$- and $d-$wave
symmetry on the background of spin density wave (SDW). We show that the SDW
coherence factors renormalize the momentum dependence of the superconducting
(SC) gap, yielding a SC state with an \emph{unconventional} s-wave symmetry.
Interband Cooper pair scattering stabilizes superconductivity in both
symmetries. With increasing SDW order, the s-wave state is more strongly
suppressed than the d-wave state. Our results are universally applicable to
two-dimensional systems with a commensurate SDW.
