  We study the contributions of the non-standard neutrino interactions (NSIs)
to the rare meson decays of $K^{+}\to \pi^{+} \nu\bar{\nu}$ and $D^{+}\to
\pi^{+} \nu\bar\nu$. We show that both decays could provide strong constraints
on the free parameters in the NSIs. We point out that the branching ratio of
$D^{+}\to \pi^{+} \nu\bar\nu$ could be at the level of $10^{-8}$.
