Smallness of neutrino masses can be explained by introducing a tiny vacuum expectation value of an extra-Higgs doublet which couples to right-handed neutrinos (\(N_R\)). This situation is naturally realized in \(\nu\)-Two Higgs Doublet Model (\(\nu\)THDM), where a TeV-scale seesaw mechanism can work well. We investigate observable phenomenology of \(\nu\)THDM at LHC and ILC experiments. Charged Higgs boson (\(H^\pm\)) in \(\nu\)THDM is almost originated from the extra-Higgs doublet and its coupling strength to neutrinos are not small. Then this model induces rich phenomenology at the LHC, for example, when \(m_{H^\pm}^{} < M_N\), observable charged tracks can be induced from long lived charged Higgs. On the other hand, when \(m_{H^\pm}^{} > M_N\), right-handed neutrinos can be long-lived, and secondary vertices may be tagged at the LHC. The \(\nu\)THDM also predicts observable lepton number violating process at the ILC.