Negative ion photoelectron spectra of ortho (o-), meta (m-), and para (p-) deprotonated benzonitrile (o-, m-, p-C6H4(CN)-) isomers as well as the associated thermochemical values corresponding to deprotonation at o-, m-, and p-positions in C6H5(CN) are presented. Quantum mechanical results based on the density functional theory (DFT) utilizing the aug-cc-pVQZ basis set indicate that the o-, m-, p-C6H4(CN)● radicals have electron affinity values (EAs) of 1.901, 1.778, and 1.789 eV, respectively. The computed Franck-Condon (FC) factors give rise to o-, m-, and p-C6H4(CN)- negative ion spectra with FC active ring distortion vibrational modes with harmonic vibrational frequencies of ∼450, 760, and 1000 cm-1 as the dominant vibrational progressions. Deprotonation at the o-, m-, and p-positions in C6H5(CN) results in calculated gas-phase acidity values (ΔacidH298Ko) of 383.9, 385.7, and 385.3 kcal mol-1, respectively. The calculated ΔacidH298Ko is in close agreement with the previously reported high-pressure mass spectrometry experimental value of 383.4.0 ± 4.4 kcal mol-1. The computed ΔacidH298Ko and EAs are utilized to estimate the bond dissociation energy (DH298(H-C6H4CN)) associated with the formation o-, m-, and p-C6H4(CN)● using the negative ion thermochemical cycle: DH298(C6H5CN) = ΔacidH298Ko (H-C6H4(CN) + EA (C6H5CN)● - IP(H). The respective values of DH298(H-C6H4CN) corresponding to the formation of ortho, meta, and para C6H4(CN) radicals are 114.15, 113.11, and 113.51 kcal mol-1.