In today's world, an antimicrobial agent that is environmentally, economically acceptable and suitable for human health is very much needed. In this paper, the effectiveness of the list of Nim plants (l. Azadirachta indica) as an antimicrobial agent for the processing of textile materials (knit) from cotton and lyocell fibers was investigated. For the purposes of the research, a dry extract of the leaves of the Nim plant was used, which was prepared in the form of alcoholic solutions of a defined concentration and used in a defined ratio for the processing of knit. The samples were pre-treated with mordant (KAl(SO4)2 and oxygen and argon plasma under defined conditions, after which the treatment was carried out by exhaustion from the bath with natural colored extract of optimum concentration, with and without mordant, different concentrations. After processing, the macrostructure analysis of the sample surfaces was performed on the example of a USB microscope Dino-lite, the analysis of antimicrobial efficacies using a qualitative microbiological test, and colorimetric analysis of solutions and staining of samples, with absorption and remission spectrophotometer. Yellow tones are obtained on samples of knits from lyocell fibers, and greenish tones were obtained on samples of cotton knits. Plasma pretreated samples (without mordant) give the best results of antimicrobial efficacy against target bacterias Staphylococcus aureus and Klebsiella pneumoniae. Analysis of the solution using an absorption spectrophotometer confirmed the compound nimbolid, which is responsible for the antibacterial properties of neem leaves, and chlorophyll a - responsible for coloring the extract. Based on the obtained results, it can be concluded that Nim is a safe, ecologically and economically suitable natural agent with good antimicrobial activity, which can be used as a natural dye for cellulosic materials.