The effect of alkyl chain length of chelating reagents on the complexation kinetics of 8-quinolinol (HQ) and 5-alkyloxymethyl-8-quinolinol (HCnQ; n = 1, 2, 3, 5, 8) with transition metal ions (M2+: Ni2+, Zn2+) at liquid-liquid interfaces is studied by dynamic interfacial tensiometry. A decrease in the dynamic interfacial tension is caused by the interfacial adsorption of a 1:1 complex (M(CnQ)+). The interfacial complexation kinetics for Zn2+ is controlled by the diffusion of ligands from the bulk organic phase to the : interface. For Ni2+, the kinetics is also diffusion-controlled for the ligands with short alkyl chains; however, it is controlled by the complexation reaction at the interface for those having longer alkyl chains. The interfacial complexation rate is found to be faster for Zn2+ than for Ni2+, and it correlates closely with the partition coefficient of the ligands. For the reaction-controlled complexation kinetics, a new procedure for calculating the interfacial complexation rate constant (k1) is proposed, and k1 values for the reaction with Ni2+ at the heptane-water interface are calculated as 1.7 × 10-5 m s-1 M-1 (1 M = 1 mol dm-3) for HC5Q and 2.2 × 10-5 m S-1 M-1 for HC8Q.