Dark matter (DM) particles are predicted to decay into Standard Model particles which would
produce signals of neutrinos, gamma-rays, and other secondary particles. Neutrinos provide an
avenue to probe astrophysical sources of DM particles. We review the decay of dark matter
into neutrinos over a range of dark matter masses from MeV to ZeV. We examine the expected
contributions to the neutrino flux at current and upcoming neutrino and gamma-ray experiments,
such as Hyper-Kamiokande, DUNE, CTA, TAMBO, and IceCube-Gen2. We consider galactic
and extragalactic signals of decay processes into neutrino pairs, yielding constraints on the dark
matter decay lifetime that ranges from 𝜏 ∼ 1.2 × 10^21 s at 10 MeV to 1.5 × 10^29 s at 1 PeV.