Liquid–liquid extraction and separation of samarium(III) were carried out by using 0.025 mol dm−3 2-octylaminopyridine(2-OAP) in xylene at 298 K. The extraction behavior of samarium was studied as a function of pH, weak acid concentration, extractant concentration, diluent, and equilibration time. Samarium was quantitatively extracted at pH 7.5 to 10.0 from 0.01 mol dm−3 sodium salicylate solution with 0.025 mol dm−3 2-OAP. The possible composition of the extracted species in organic phase has been determined by using model of slope analysis method and extraction mechanism was found to proceed via an anion exchange mechanism. The stripping efficiency was found to be quantitative in HNO3, HCl and CH3COOH. The robustness of the procedure was demonstrated by the average recoveries obtained (>99.6%) for samarium(III) extraction in the presence of several cations and anions which are commonly associated with it. The proposed method facilitates the separation and determination of samarium(III) from binary and synthetic mixtures. The various thermodynamic functions like free energy (ΔG), enthalpy (ΔH) and entropy (ΔS) of extraction mechanism were discussed.