The electronic spectroscopy and photochemistry of the trans isomers of 3-(N-phenylamino)stilbene (nil 3-(N-methyl-N-phenylamino)stilbene (m1d), 3-(NN-diphenylamino)stilbene (nille), and 3-(N-(2,6-dimethylphenyl)amino)stilbene (m1f) and their double-bond constrained analogues m2a-m2c and m2e are reported. When compared with trans-3-aminostilbene (m1a), m1c-m1e display a red shift of the S-0 -> S-1 absorption and fluorescence spectra, lower oscillator strength and fluorescence rate constants, and more efficient S, T, intersystem crossing. Consequently, the N-phenyl derivatives m1c-m1e have lower fluorescence quantum yields and higher photoisomerization quantum yields. The corresponding N-phenyl substituent effect in m2a-m2e is similar in cyclohexane but smaller in acetonitrile. This is attributed to the weaker intramolecular charge transfer character for the S-1 state of m2 so that the rates for intersystem crossing are less sensitive to solvent polarity. It is also concluded that N-phenyl substitutions do not change the triplet mechanism of photoisomerization for m1 in both nonpolar and polar solvents. Therefore, the "m-amino conjugation effect" reinforces the "m-amino effect" on fluorescence by further reducing its rate constants and highlights the N-phenyl-enhanced intersystem crossing from the "amino-conjugation effect" by making S-1 -> T-1 the predominant nonradiative decay pathway.