The Inert Doublet Model is an intriguing extension of the SM scalar sector. It is a two Higgs doublet model with a discrete Z_2 symmetry, that renders the lightest particle from the second doublet stable and therefore provides a good dark matter candidate. Current constraints on the model as well as discovery prospects at current and future searches will be discussed, with a special emphasis on future $e^+e^-$ machines with center-of-mass energies up to 3 TeV (CLIC). A large set of proposed benchmark points promise to be testable with high significances.