  We investigate the phenomenology of the light charged and neutral scalars in
Inert Doublet Model at future $e^+ e^-$ colliders with center of mass energies
of 0.5 and 1 TeV, and integrated luminosity of 500~fb$^{-1}$. The analysis
covers two production processes, $e^{+}e^{-} \rightarrow H^{+}H^{-}$ and
$e^{+}e^{-}\rightarrow AH$, and consists of signal selections, cross section
determinations as well as dark matter mass measurements. Several benchmark
points are studied with focus on $H^{\pm} \rightarrow W^{\pm}H$ and $A
\rightarrow ZH$ decays. It is concluded that the signal will be well observable
in different final states allowing for mass determination of all new scalars
with statistical precision of the order of few hundred MeV.
