The Compact Linear Collider (CLIC) is a proposed TeV-scale high-luminosity electron-positron collider, an attractive option for the next large facility at CERN. Already the first CLIC stage, with energy of 380 GeV, will allow us to study the Higgs boson properties with very high precision. These measurements can also result in direct or indirect discovery of "new physics", Beyond the Standard Model (BSM) phenomena, which could help us to understand the nature of dark matter (DM). Higgs boson decays with emission of invisible DM particles can be the only way to observe "new physics" effects at low energy scales and establish connection between Standard Model (SM) and BSM sectors. We studied the possibility of measuring invisible Higgs boson decays with experiment at CLIC running at 380 GeV. The analysis is based on the WHIZARD event generation and fast simulation of CLIC detector response with DELPHES. The approach consisting of a two step analysis was used to optimize separation between signal and background processes. First, a set of preselection cuts was applied to remove background events not consistent with expected signal signature; then, the multivariate analysis methods were applied to optimise significance of observations. We estimated the expected limits on the invisible decays of the 125 GeV Higgs boson, as well as the cross section limits for production of an additional neutral Higgs scalar, assuming its invisible decays, as a function of its mass. Extracted model-independent branching ratio and cross section limits were then interpreted in the framework of the vector-fermion dark matter model to set limits on the mixing angle between the SM-like Higss boson and the new scalar of the "dark sector".

CLIC running at 380 GeV can constrain the invisible decays of the SM Higgs boson to below 1%. Branching ratio and cross section limits can be translated to the limits on model parameters in different BSM scenarios.