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The concept of photocaging represents a promising approach to acquire spatiotemporal control over molecular bioactivity. To apply this strategy to pyridinylimidazole-based covalent JNK3 inhibitors, we used acrylamido-<i>N</i>-(4-((4-(4-(4-fluorophenyl)-1-methyl-2-(methylthio)-1<i>H</i>-imidazol-5-yl)pyridin-2-yl)amino)phenyl)benzamide (<b>1</b>) as a lead compound to design novel covalent inhibitors of JNK3 by modifying the amide bond moiety in the linker. The newly synthesized inhibitors demonstrated IC₅₀ values in the low double-digit nanomolar range in a radiometric kinase assay. They were further characterized in a NanoBRET^TM intracellular JNK3 assay, where covalent engagement of the target enzyme was confirmed by compound washout experiments and a loss in binding affinity for a newly generated JNK3(C154A)-NLuc mutant. The most potent compound of the series, <i>N</i>-(3-acrylamidophenyl)-4-((4-(4-(4-fluorophenyl)-1-methyl-2-(methylthio)-1<i>H</i>-imidazol-5-yl)pyridin-2-yl)amino)benzamide (<b>13</b>), was equipped with a photolabile protecting group leading to a nearly 10-fold decrease in intracellular JNK3 binding affinity, which was fully recovered by UV irradiation at a wavelength of 365 nm within 8 min. Our results highlight that photocaged covalent inhibitors can serve as a pharmacological tool to control JNK3 activity in live cells with light.