Abstract The magnetic and orbital moments of Co atoms in YCo 5− x Ni x were computed with the Haydock recursion method in a self-consistent procedure. The decrease in magnetic moment per formula unit with increase in Ni concentration is related to the peculiarities of the density of states for x ≠ 0 and to the decrease in exchange splitting. The transition temperatures were computed in the framework of the spin-fluctuations theory. There are large orbital moments on both Co sites for all the compounds. The orbital polarization was considered as an effective spin-orbit interaction.