Improvement of technologies in the field of creation of new metallic materials is, inter alia, by increasing the number of alloy components. Development of the new class of multicomponent metal compositions – so called high entropy alloys – started in recent years. The basis of these alloys is a composition of at least five basic metals, the content of each of them varies from 5 to 35 atomic %. The objects of the study were multicomponent electrochemical coatings nickel-cobalt-iron-tungsten-carbon (Ni-Co-Fe-W-C) deposited from electrolytes based on the molten carbamide as a solvent. The concentration of components in the electrolyte was (wt. %): NiCl2 – 12; CoCl2 – 3; FeCl2 – 5; Na2WO4 – 4. Coatings based on an electrochemical alloy of the Ni-Co-Fe-W system are deposited in the current density range of 5..10 mA/cm2. With a current density of 8..10 mA/cm2, the coating contains (wt. %): Ni – 58.61; Co – 19.14; Fe – 20.67 and W – 0.24. An increase in the current density (15.25 mA/cm2) leads to the formation of composite coatings of the nickel-iron-cobalt-tungsten-carbon system. The coating deposited at a current density of 15 mA/cm2 contains (wt. %): Ni – 58.13; Co – 10.62; Fe – 28.57; W – 1.49 and carbon – 1.19.  Annealing the coatings at a temperature of 575 K does not change their microstructure and phase composition throughout the annealing time interval. The microhardness of coatings increases from 4.6 to 6.1 GPa after 24 hours of annealing. This correlates with the change in the lattice parameter of the complex-doped "solid solution" based on nickel: the change of the latter from 3.5241 to 3.5261 Å also occurs after 24 hours of annealing. With an increase in the annealing temperature to 675 K, the lattice parameters of the complex-doped solid solution correlate with changes in the microhardness of the coatings as in the case of 575 K. Microhardness of coatings reaches 11 GPa after 4 hours of annealing. Annealing of the coatings is accompanied by a change in their phase composition, not microstructure. According to X-ray diffraction analysis, the initial state of Ni-Co-Fe-W-C coatings is a complex solution, based on a face-centered cubic lattice of nickel, in which there are regions with a complex-doped solid solution structure based on α-Fe. After two- and four-hour annealing, reflexes of solid-solution on the basis of the bcc lattice of iron disappear. After 8-hour annealing, additional reflections of the solid solution based on the hcp cobalt lattice appear instead of them. The presence of dispersed carbon particles in the coating structure shows that the solvent (carbamide) participates in the electrocrystallization of the coating.  An increase in the lattice parameter of a solid solution during annealing (up to 2 hours) is due to the formation of a solid solution with high nickel content and to the diffusion redistribution of cobalt atoms in a complex-doped solid solution. The subsequent decrease in the lattice parameter of the same after two hours of annealing is caused by the decomposition of a solid solution based on the fcc lattice of nickel and the formation of a solid solution based on the hcp cobalt lattice. The change in the phase composition of the coatings for 2..8 hours, shows that electrochemical alloys have a nonequilibrium microstructure at the nanoscale level, and the redistribution of the components of the solid solution occurs under the diffusive displacement of atoms at short distances, in contrast to metallurgical nickel-base alloys in which solid solutions decay processes occur at higher temperatures (775..975 K) for tens of hours. A similar character of the change in the microstructure, the lattice parameter of the solid solution, and the microhardness shows that the formation of the structure of the Ni-Fe-Co-W-C electrochemical alloys proceeds at the nanoscale level at the stage of nucleation and then crystallization during the independent genesis of nickel and iron. Their subsequent growth proceeds through the addition of Ni, Fe, Co, W (and, in some measure, carbon) atoms.  The nature of the change in the microhardness, the microstructure of the electrochemical materials of the Ni-Fe-Co-W-C system, the phase composition of the materials formed during annealing, shows that the mechanism of structural-phase transformations (and hardening) of electrochemical alloys is different from the same in metallurgical alloys that do not harden during low-temperature annealing.