A binary extractant based on trialkylbenzylammonium and higher isomeric α,α'-branched carboxylic acids (R4NA) was synthesized. The extraction of uranyl nitrate with 0.52 M solutions of R4NA and R4NNO3 in toluene was studied. The extraction isotherms were constructed. The physicochemical and mathematical models of the extraction of uranyl nitrate were developed. The following extractable species were shown to be formed in the organic phase: (R4N)2[UO2(NO3)4], R4N[UO2A(NO3)2], and (R4N)2[UO2A2(NO3)2] The extraction constants were calculated. The organic phase was examined by IR spectroscopy.