A search for Higgs boson production in association with a W or Z boson, in the H2!W W * decay channel, is performed with a data sample collected with the ATLAS detector at the LHC in proton-proton collisions at centre-of-mass energies \(\sqrt{s}=7 \) TeV and 8 TeV, corresponding to integrated luminosities of 4.5 fb-1 and 20.3 fb-1, respectively. The WH production mode is studied in two-lepton and three-lepton final states, while two- lepton and four-lepton final states are used to search for the ZH production mode. The observed significance, for the combined W H and ZH production, is 2.5 standard deviations while a significance of 0.9 standard deviations is expected in the Standard Model Higgs boson hypothesis. The ratio of the combined W H and ZH signal yield to the Standard Model expectation, [mu]V H, is found to be [mu] V H = 3.0-1.1+1.3 (stat.)-0.7 +1.0 (sys.) for the Higgs boson mass of 125.36 GeV. The W H and ZH production modes are also combined with the gluon fusion and vector boson fusion production modes studied in the H 2!W W * 2!l[nu]l[nu] decay channel, resulting in an overall observed significance of 6.5 standard deviations and [mu]ggF + VBF + VH = 1.16-0.15+0.16 (stat.) -0.15+0.18 (sys.). The results are interpreted in terms of scaling factors of the Higgs boson couplings to vector bosons ([kappa]V) and fermions ([kappa]F); the combined results are.