Determining the stoichiometry of Eu(III) to N,N,N′,N′-tetraoctyldiglycolamide (TODGA) in the organic phase containing TODGA in n-dodecane (n-DD) is a challenging job due to the formation of third phase prior to the maximum loading of Eu(III) in the organic phase. The phase modifier tri-n-butyl phosphate (TBP) has been added to the organic phase to minimize and prevent the undesirable third phase formation. Even though the added TBP prevented the third phase, the loading behavior of Eu(III) in TODGA + TBP/n-DD and the role of TBP in altering the stoichiometry of Eu(III) to TODGA is unknown so far. To unravel the role of TBP at higher loadings of Eu(III) in the organic phase, the extraction behavior of Eu(III) from nitric acid solution was studied in a solution of 0.1 M TODGA + TBP/n-DD. The concentration of nitric acid and Eu(III) in aqueous phase, and TBP concentration in organic phase were varied in those investigations to determine the maximum loading of Eu(III) and stoichiometry of Eu(III) to TODGA in organic phase. The results revealed that the Eu(III) to TODGA stoichiometry of 1:1 could be achievable at higher concentrations of TBP in the organic phase (> 1 M), which served as a sacrificial proton acceptor during extraction. The results were supported by FTIR investigations in the loaded organic phase.