We study the Higgs sector of the U(1)'-extended MSSM with CP violation. This is an extension of the MSSM Higgs sector by one singlet field, introduced to generate the μ term dynamically. We are particularly interested in non-standard decays of Higgs particles, especially of the lightest one, in the presence of CP violating phases for μ_eff and the soft parameters. We present analytical expressions for neutral and charged Higgs bosons masses at tree and one-loop levels, including contributions

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... om top and bottom scalar quark sectors. We then study the production and decay channels of the neutral Higgs for a set of benchmark points consistent with low energy data and relic density constraints. Numerical simulations show that a Higgs boson lighter than 2m_W can decay in a quite distinctive manner, including invisible modes into two neutralinos (h->χ^0χ^0) up to 50 allowed. The branching ratio into h->bb, the dominant decay in the SM, is reduced in some U(1)' models and enhanced in others, while the branching ratios for the decays h -> τ+ τ-, h -> WW^* and h -> Z Z^*-> 4l are always reduced with respect to their SM expectations. This possibility has important implications for testing the U(1)' model both at the LHC and later at the ILC.