  We study effects of CP violation in the associated production of a charged
Higgs boson and a top quark at the LHC, $pp \to tH^\pm + X$. We calculate the
CP violating asymmetry between the total cross section for $H^+$ and $H^-$
production at next-to-leading order in the MSSM, and perform a detailed
numerical analysis. In the production the asymmetry is of the order of 20%. The
asymmetry in the production and any subsequent decay of an on-shell charged
Higgs boson is to a good approximation the sum of the asymmetry in the
production and the asymmetry in the decay. We consider subsequent decays of
$H^\pm $ to $t b$, $\nu_\tau \tau^\pm$ and $W h^0$. In the case with $H^\pm \to
t b$ decay, mainly due to CP violating box graphs with gluino, the asymmetry
can go up to $\sim$ 12%.
