  We study R-parity violating contributions to the mixing parameter $y$ for
$D^0 -\bar D^0$ and $B^0_{d,s} - \bar B^0_{d,s}$ systems. We first obtain
general expressions for new physics contributions to $y$ from effective four
fermion operators. We then use them to study R-parity contributions. We find
that R-parity violating contributions to $D^0 - \bar D^0$ mixing, and $B_{d}^0
- \bar B_{d}^0$ to be small. There may be sizable contribution to $B_s^0 -\bar
B_s^0$ mixing. We also obtain some interesting bounds on R-parity violating
parameters using known Standard Model predictions and experimental data.
