The study aimed to assess the effect of some Co(II) compounds on the production of biomass, β-carotene and astaxanthin by green microalga Haematococcus pluvialis at different stages of its life cycle. Cobalt compounds (Co(OAc)2 and CoCl2) were added to the nutrient medium of Haematococcus pluvialis on the first day of the cultivation cycle. The biomass of H. pluvialis was collected according to some conventional stages of the life cycle: day 3 - green cell stage, day 10 - brown cell stage, and day 14 - aplanospore stage. Changes in the amount of microalgae biomass were determined depending on the stage of the life cycle, as well as the content of β-carotene and astaxanthin pigments. Analysis of the data obtained in the course of a series of experiments indicates that the studied Co(II) compounds did not inhibit cell proliferation within the limits of applied concentrations. Co(II) acetate, depending on the concentration, was involved in the processes of cell multiplication and the synthesis of β-carotene. In concentrations of 1.5 and 2.0 mg/L, Co(OAc)2 stimulated biomass and astaxanthin production. CoCl2 was involved in the proliferation of microalgae cells, the green cell stage being the most sensitive to the action of the compound.