  We study an extension of the Standard Model (SM) in which two copies of the
SM-Higgs doublet which do not acquire a vacuum expectation value, and hence are
{\it inert}, are added to the scalar sector. The lightest particle from the
inert sector, which is protected from decaying to SM particles through the
conservation of a $Z_2$ symmetry, is a viable dark matter candidate. We allow
for CP-violation in this extended dark sector and evaluate the $ZZZ$ vertex and
its CP-violating form factor in several benchmark scenarios. We provide
collider signatures of this dark CP-violation in the form of potentially
observable asymmetries and cross sections for the $f\bar f\to Z^*\to ZZ$
process at both leptonic and hadronic machines.
