Two diglycolamide (DGA) derivatives having n-butyl (nBuDGA) and s-butyl (sBuDGA) groups have been used for the extraction of Am³⁺ and Eu³⁺ to study the role of alkyl chain branching on their separation behaviour. Interestingly, the selectivity between Am³⁺ and Eu³⁺ reversed upon changing the ligand from nBuDGA to sBuDGA. An opposite trend was also observed in the extraction of lanthanide ions along the series of decreasing ionic radii for these two ligands. Luminescence and FTIR studies suggest a different nature of the Eu³⁺ complexes of these two ligands. DFT studies were performed to find out the structure and the electronic distribution of the Am³⁺ and Eu³⁺ complexes of these two ligands.