In this study, a novel organic compound—naphthalen-2-yl 2-thiocyanatoacetate—was synthesized via a nucleophilic substitution reaction (SN2 mechanism) in dimethylformamide (DMF) as the solvent. The molecular structure of the synthesized compound was confirmed by infrared (IR) and nuclear magnetic resonance (NMR) spectroscopy. The compound was evaluated for its analytical properties, particularly its ability to form a colored complex with Ni(II) ions, which was investigated using a photometric detection method. A comprehensive optimization of the detection conditions was performed. Factors such as the acidity of the reaction medium (pH), the order of reagent addition, the amount of reagent, the selection of optical filter, maximum absorption wavelength (λmax), Beer’s law linearity range, molar absorptivity, Sandell sensitivity, limit of detection (LOD), equilibrium constant, and the molar ratio of the complex components were studied in detail. The results demonstrated that the synthesized compound exhibits high sensitivity, selectivity, and stability in complex formation with Ni(II) ions. The developed photometric method is simple, cost-effective, and rapid, and can be implemented using basic instrumentation. Therefore, the method shows great potential for application in environmental monitoring, industrial wastewater analysis, and trace metal detection. This work contributes to the development of novel thiocyanate-based analytical reagents and expands the toolbox for photometric determination of transition metal ions, particularly Ni(II).