Critical latitudes are believed to be a significant factor for tidal dissipation. Studies have revealed that non-linear interactions of tides occur easily at the critical latitudes, but the influence of background currents on these non-linear interactions is not well known. The latitude effects of background currents from eddies or a boundary current on tides, the internal tidal fields, internal waves, and mixing were investigated using the Regional Ocean Modeling System (ROMS). This was accomplished by shifting a small domain including a seamount from 20.6o to 38.6oS and comparing simulations with and without background currents from an eddy. Compared to the results without background currents, the kinetic energy of diurnal frequencies was unchanged for most latitudes except decreased 1-4o poleward of the critical latitude, which had a slight decrease; however, the kinetic energy of semidiurnal frequencies and the high frequency harmonics (≥3 cpd) increased with the presence of the mesoscale currents, especially between the latitude range of O1 and K1 critical latitudes. Spectral and non-linear analyses indicated that the mesoscale currents broadened the critical latitude range and enhanced energy transfers from diurnal frequencies to semidiurnal and high frequencies and from waves with low modes to high modes. Correspondingly, local diffusivities also increased dramatically, roughly a factor of 20, when mesoscale currents were present. The impacts of mesoscale currents on the broadening of the critical latitude range and enhancement of non-linear interactions were attributed to the additional relative vorticity and near-inertial internal waves generated by mesoscale currents.