  We investigate the impact of unparticle physics on the annihilation of relic
neutrinos with the neutrinos identified as primary source of ultra high energy
(UHE) cosmic ray events, producing a cascade of photons and charged particles.
We compute the contribution of the unparticle exchange to the cross-sections
$\nu \bar\nu\to\gamma \gamma$ and $\nu \bar\nu\to f \bar f$ scattering. We
estimate the neutrino photon decoupling temperature from the reaction rate of
$\nu \bar\nu\to\gamma \gamma$. We find that inclusion of unparticles can in
fact account for the flux of UHE cosmic rays and can also result in the
lowering of neutrino - photon decoupling temperature below the QCD phase
transition for unparticle physics parameters in a certain range. We calculate
the mean free path of these high energy neutrinos annihilating themselves with
the relic neutrinos to produce vector and tensor unparticles.
