Nucleophilic addition reactions of benzylamines (BA; $XC_6H_4CH_2NH_2$) to ethyl-${alpha}$-cyanocinnamates (ECC;$YC_6H_4CH$=C(CN)COOEt) have been investigated in acetonitrile at $30.0^{circ}C$. The rate is first order with respect to BA and ECC. The rate is slower than that expected from the additive effect of ${sigma}^-$ or $R^-$ for the activating groups (CN and COOEt). Natural. bond orbital ${pi}^{ast}_{c=c}$ calculations show that the contribution of COOEt group may not be fully effective despite the coplanar molecular structure. The selectivity parameters including the cross-interaction constant (${ ho}_{xy}$ = -0.22) indicate that the addition occurs in a single step. The kinetic isotope effects ($k_H/k_D$=2.5-2.8) involving deuterated BA ($XC_6H_4CH_2ND_2$) nucleophiles and activation parameters (${Delta}H^{ eq}=4{sim}6;kcal;mol^{-1};{Delta}S^{ eq}=-45{sim}-52;e.u.$) suggest a cyclic transition state in which N-$C_{alpha}$ and H-$C_{eta}$ bonds are formed concurrently.