The fermentation of Tagetes patula L. flowers infusion by native microorganisms has been studied. The composition of marigold flower microorganisms, which includes yeasts, bacteria, and microscopic molds was determined. It was established that yeasts from the genera Saccharomyces, Brettanomyces, and Rhodotorula, along with lactic acid bacteria from the genera Lactobacillus and Leuconostoc participate in the spontaneous fermentation of the infusion. The influence of sugar and citric acid concentrations on the fermentation duration, as well as physicochemical, microbiological, and organoleptic indicators of the fermented infusion, was demonstrated. It was established that acidification with citric acid effectively promotes fermentation of the infusion primarily at a sugar concentration of 7.0 %. The pH value significantly impacts the dynamics of spontaneous fermentation and the properties of the fermented marigold infusion. It was found that increasing the initial citric acid concentration and lactic acid adversely affects yeast, particularly Saccharomycetes, during the fermentation of the marigold infusion.