  We study the effects of heavy Majorana neutrinos on the Higgs sector of the
MSSM via radiative corrections. We work within the SUSY context where the MSSM
particle content is enlarged with right handed neutrinos and their
corresponding SUSY partners, the sneutrinos, and where compatibility with
neutrino data is required. We compute the one-loop corrections to the mass of
the lightest MSSM CP-even neutral Higgs boson from Majorana neutrinos and their
SUSY partners and assume a seesaw mechanism of type I for neutrino mass
generation. A negative and sizeable Higgs mass correction of up to -5 GeV is
found for a heavy Majorana mass of up to 10^{15} GeV. This negative correction
can grow up to several tens of GeV if the soft SUSY breaking mass associated to
their sneutrino partners is simmilarly heavy as the Majorana mass.
