The aminolysis reactions of phenyl N-benzyl thiocarbamate with benzylamines in acetonitrile at $50.0^{circ}C$ are investigated. The reactions are first order in both the amine and the substrate. Under amine excess, pseudo-first coefficient ($k_{obs}$) are obtained, plot of $k_{obs}$ vs free amine concentration are linear. The signs of ${ ho}_{XZ}$ (< 0) are consistent with concerted mechanism. Moreover, the variations of $ ho_X$ and $ ho_Z$ with respect to the sustituent in the substrate and large ${ ho}_{XZ}$ value indicate that the reactions proceed concerted mechanism. The normal kinetic isotope effects ($k_H/k_D$ = 1.3 ~ 1.5) involving deuterated benzylamine nucleophiles suggest a hydrogen-bonded, four-centered-type transition state. The activation parameters, ${Delta}H^ddagger$ and ${Delta}S^ddagger$, are consistent with this transition state structure.