  We analyze the role of sterile neutrinos in the framework of the $\mu\nu$SSM,
where the presence of right-handed neutrinos provides a simultaneous solution
to $\mu$- and $\nu$-problems in supersymmetry. We adopt a minimalistic
approach, reproducing light neutrino masses and mixing angles at tree level
using just two right-handed neutrinos as part of the seesaw mechanism. A third
right-handed neutrino does not contribute significantly to the mass of the
three active ones, behaving as a sterile neutrino with a mass in the range
keV$-$MeV. Furthermore, a sterile neutrino of about $10$ keV can be a good
candidate for dark matter with a lifetime larger than the age of the Universe.
In particular, the three-body decay to active neutrinos gives the dominant
contribution to its lifetime. The one-loop decay to gamma and active neutrino
is subdominant, but relevant for observations such as astrophysical X-rays. We
find regions of the parameter space of the $\mu\nu$SSM, with different values
of the sterile neutrino mass, fulfilling not only these constraints but also
collider constraints from the Higgs sector.
