Objective. Study the biological activity of nickel nanoparticles (Ni NPs) against pathogenic viruses and fungi, pathogens of farm animals and plants, investigate their bactericidal and growthregulating properties. Methods. Virological, microbiological and statistical. Virucidal activity of NiNPs was evaluated by the difference of virus titres in the control and under the action of NPs, bactericidal — by the difference of bacterial titres, fungicidal and fungistatic — by the difference of diameters of fungal colonies, growth-regulating — by the difference in leaf blade length and roots ofgerms of winter wheat. The antiviral activity of NPs was determined in the culture of versenalisedembryonic porcine kidney cells. Bactericidal activity was investigated in a liquid digest medium.Fungistatic activity was determined on wort agar. Wheat germs were germinated in Petri dishesaccording to generally accepted methods. The viral titre was calculated by Reed-Muench method.The bacterial titre was determined by seeding the suspensions on agar medium. Statistical processing was performed in Microsoft Office Excel and statsoft STATISTICA 12, using Student's t-test,post-hoc tests: Fisher’s least significant difference test and Duncan’s new multiple range test.Results. It was found that Ni NPs show high virucidal activity against Teschovirus A strainDniprovskyi-34, reducing the virus titre by 2.46 lg TCD50/cm3, and have a chemotherapeutic indexof 4. Ni NPs have low fungistatic activity against Acremonium cucurbitacearum 502, reducing theaverage diameter of colonies by 6.58 to 20.22 %. Regarding Acremonium strictum 048 and Fusarium sp. 072, Ni NPs have a slight stimulating activity, increasing the average diameter of the colonies by 10.18 to 12.44 % and 14.84 to 22.18 %, respectively. Under the action of Ni NPs, the titre ofBacillus subtilis ІМВ В-7023 and Pseudomonas chlororaphis subsp. aureofaciens UKM B-306(2687) upon the cultivation of bacteria in meat-peptone broth significantly (by 80.96 to 82.77 %and 15.67 to 36.39 %, respectively) increases. Ni NPs exhibits growth-promoting properties onwheat germs, increasing the average length of leaf blades and roots by 41.79 and 36.76 %, respectively. Conclusion. According to the study findings, Ni NPs cannot be recommended for the creation of antifungal preparations. Further research is needed to develop Ni NP-based antiviral preparations, virucidal and disinfecting agents, growth- regulating products for cultivated plants, and toincrease the titre of beneficial soil bacteria.