  Several theories of particle physics beyond the Standard Model consider that
neutrinos can decay. In this work we assume that the standard mechanism of
neutrino oscillations is altered by the decay of the heaviest neutrino mass
state into a sterile neutrino and, depending on the model, a scalar or a
Majoron. We study the sensitivity of the forthcoming KM3NeT-ORCA experiment to
this scenario and find that it could improve the current bounds coming from
oscillation experiments, where three-neutrino oscillations have been
considered, by roughly two orders of magnitude. We also study how the presence
of this neutrino decay can affect the determination of the atmospheric
oscillation parameters $\sin^2\theta_{23}$ and $\Delta m_{31}^2$, as well as
the sensitivity to the neutrino mass ordering.
