The paper presents the results of microbiological tests of composite membranes made of cellulose (CEL) with graphene oxide (GO) admixture. At the beginning, the antibacterial properties of the GO in aqueous solutions of various concentrations (0.001; 0.01; 0.1% w/w) were studied, and the obtained results allowed to use GO as an additive to cellulose membranes. The solution used to prepare the membranes was a 5% cellulose solution (CEL) in 1-ethyl-3-methylimidazolium acetate (EMIMAc), into which various amounts of graphene oxide (GO) dispersed in N,N-dimethylformamide (DMF) were added (0.5 ÷ 28.6 % of GO). From this solution, composite membranes were formed using phase inversion method. It was observed that the GO addition influences the process of membrane formation and their physicochemical properties. The obtained membranes were subjected to microbiological tests using the Gram-negative bacteria (Escherichia coli), Gram-positive bacteria (Staphylococcuc aureus) and fungi (Candida albicans). It was observed that the GO addition to the cellulose membrane (GO/CEL) inhibited the growth of bacteria and fungi, and the biological activity as dependent on the type of living organism and the size of GO particles.