In this work it is presented a fluid-structure-interaction modelling methodology, of an oil & gas deepwaters manifold. The methodology couple oil & gas flows, in the piping system of the manifold, of typical oil & gas production in wells in the Gulf of Mexico, with the structure of the manifold. This to study the structural behavior of the manifold with the flow of oil & gas. Dynamic modal analyses were made to evaluate critical vibration modes of manifold components, along with their natural frequencies. Harmonic analyses were performed to evaluate displacement amplitudes, velocity amplitude, and acceleration amplitudes. of the manifold. Afterwards, the stresses and strains were evaluated under two conditions: with the piping system only, and with the full manifold assembly. The analyses were undertaken at water depths: 3000 m, 2000 m and 1000 m. And the higher natural frequency was presented in the flow metering devices, in the 10th vibration mode, at 20.77 Hz, which was the same for oil & gas flows. However, the amplitudes of displacement, velocity and acceleration were higher for gas flow. The higher stresses were in the rigid structure of the manifold; however, they are below the yield stress of manifold steel