The present equilibrium study deals with the reactive extraction of 4-oxopentanoic acid [levulinic acid] from an aqueous solution by N,N-dioctyloctan-1-amine [tri-n-octylamine (TOA)] at a constant concentration of 0.573 kmol.m(-3) in a wide range of diluents such as [n-decane, decane-1-ol, n-decane + decane-1-ol (1:1 v/v), toluene, 4-methylpentan-2-one (MIBK), and dichloromethane (DCM)] at isothermal conditions ((298 +/- 1) K). The physical extraction of levulinic acid with pure diluents is also carried out. The effect of acid concentration (0.10 mol.kg(-1) to 0.75 mol.kg(-1)) and type of diluent on the recovery of levulinic acid from aqueous solution are determined. Mathematical modeling based on mass action law is used to estimate overall equilibrium constants (K-E), stoichiometry of reaction, and individual equilibrium constants (K-11 and K-21) for 1:1 and 2:1 complexes between acid and TOA. Further, the experimentally determined distribution coefficients (K-D) are correlated predicted ones by the linear solvation energy relationship (LSER) model based on solute-solvent interaction parameters. The extraction power of TOA increases in the order of DCM >= decan-1-ol > MIBK > n-decane + decan-1-ol (1:1 v/v) > toluene > n-decane with the highest extraction efficiency, 98.7 %.