Nucleophilic addition reactions of benzylamines (BA; $XC_6H_4CH_2NH_2$) to $alpha-cyano-eta$-phenylacrylamides (CPA; $YC_6H_4CH=C(CN)CONH_2$) have been investigated in acetonitrile at 25.0 ${^{circ}C}$. The rate is first order with respect to BA and CPA and no base catalysis is observed. The addition of BA to CPA occurs in a single step in which the addition of BA to $C_{eta}$ of CPA and proton transfer from BA to $C_{alpha}$ of CPA take place concurrently with a four-membered cyclic transition state structure. The magnitude of the Hammett ($ ho_X$) and Bronsted ($eta_X$) coefficients are rather small suggesting an early tansition state (TS). The sign and magnitude of the crossinteraction constant, $ ho_XY$ (= ?D0.26), is comparable to those found in the normal bond formation processes in the $S_N2$ and addition reactions. The normal kinetic isotope effect ($k_H/k_D;{gt}$ 1.0) and relatively low ${Delta}H^{ eq}$ and large negative ${Delta}S^{ eq}$ values are also consistent with the mechanism proposed.