  The leading corrections to electroweak precision observables in the MSSM with
non-minimal flavor violation (NMFV) are calculated and the effects on M_W and
sin^2 theta_eff are analyzed. The corrections are obtained by evaluating the
full one-loop contributions from the third and second generation scalar quarks,
including the mixing in the scalar top and charm, as well as in the scalar
bottom and strange sector. Furthermore the leading corrections to the mass of
the lightest MSSM Higgs boson, m_h, is obtained. The electroweak one-loop
contribution to M_W can amount up to 140 MeV and up to 70x10^{-5} for sin^2
theta_eff, allowing to set limits on the NMFV parameters. The corrections for
m_h are not significant for moderate generation mixing.
