  The mixing of $K^0-\bar{K^0}$, $D^0-\bar{D^0}$ and
$B_{(s)}^0-\bar{B^0_{(s)}}$ provides a sensitive probe to explore new physics
beyond the Standard Model. The scale invariant unparticle physics recently
proposed by Georgi can induce flavor-changing neutral current and contribute to
the mixing at tree level. We investigate the unparticle effects on
$B^0-\bar{B^0}$ and $D^0-\bar{D^0}$ mixing. Especially, the newly observed
$D^0-\bar{D^0}$ mixing sets the most stringent constraints on the coupling of
the unparticle to quarks.
