The solvation structures of tetraethylammonium bromide and tetrafluoroborate (TEABr and TEABF(4)) in aqueous binary solvents with ethanol (EtOH), 2,2,2-trifluoroethanol (TFE), and acetonitrile (AN) have been clarified by molecular dynamics (MD) simulations. In addition, H-1 and C-13 NMR chemical shifts of the H and C atoms within TEA(+) in the binary solvents have been measured as a function of the mole fraction of the organic solvent, x(OS). The variations of the chemical shifts with an increase in x(OS) were interpreted according to the solvation structures of TEA(+), Br-, and BF4- obtained from the MD simulations. It has been found that TEABF(4) at 130 mmol dm(-3) cannot be dissolved into the EtOH and TFE solvents above x(OS) approximate to 0.7 and 0.6, respectively, while TEABr can be done in both solvents. Interestingly, TEABr and TEABF(4) at the concentration can be dissolved in the AN solvents over the entire x(OS) range. The solvation of TEA(+), Br-, and BF4- in each solvent has been discussed in terms of the electrostatic force, the weak hydrogen bond of C-H center dot center dot center dot F-C, and the dipole-dipole interaction.