We discuss the potential of detecting thermal neutrinos from matter-rich binary mergers, via a decades-long multi-messenger campaign involving a Mt-scale water Cherenkov neutrino detector and one or more next generation gravitational wave detectors, capable of observing mergers up to redshift z ∼ 2. The search of neutrinos in time-coincidence with gravitational wave detections will allow to identify single neutrinos from individual mergers above the background, and to study their distributions in energy, redshift and type (double neutron-star or neutron-star-black hole merger) of the candidate sources. We find that, for merger rates consistent with current LIGO-Virgo constraints, and for a 100 Mt · yr exposure, between O(10 −1 ) and O(10) neutrino events are expected. For extreme cases of mergers with more than 10 52 ergs emitted inνe, the number of events can be as large as ∼ 100, with sensitivity to mergers up to redshift z ∼ 0.5 or so. Such scenarios can already be tested with a 10 Mt · yr exposure, resulting in constraints on the post-merger evolution of the systems being considered.