Cobalt (II) plays an important role in biological processes in the body and is an indicator of some diseases. This requires constant monitoring of anthropogenic pollutants and the migration of toxic substances in the environment. We studied the possibility of using 2-piperidinomethyl-4- (3-methylcyclohexyl) phenol (L) for photometric determination of cobalt (II). Cobalt (II) forms a colored complex with L, which dissolves in chloroform. In a single extraction with chloroform, 97.6% of cobalt is recovered as a complex. The complex is extracted at pH 4.2-5.5. Optimal conditions for the formation and extraction of the complex are 0.8×10-3 mol/l, concentration L. The extract of the complex obeys Beer‘s law at a concentration of 0.03-3.6 μg ml of cobalt. The maximum optical density is reached within 5 minutes. The optimal Vaq/Vorg value is 5/5-80 5. The molar absorption coefficient is ℇ548 = 3.25 × 104. The stoichiometry of the complexes under study was established by the methods of equilibrium shift and relative yield. The ratio of the components in the Co: L complex = 1: 2. It was found that colored complexes with L also form ions Fe (III), V (IV), Cu (II), Ni (II), Mo (VI), Pt (II), Mn (II), Cd (II), Zn (II) and Pd (II). The selectivity of the determination increases significantly in the presence of masking reagents or when the pH of the medium changes. Based on the results of spectrophotometric studies of cobalt (II) with L, methods have been developed for the determination of cobalt in plants (beans: 0.20 ± 0.0053 μg kg Co; peas: 0.11 ± 0.0040 μg kg Co) in wastewater (0.45 ± 0.05) μg l Co) and bottom sediments (1.92 ± 0.04 μg l Co).