Anthelmintics are pharmaceuticals that have wide application in veterinary and human medicine for the treatment of infections caused by intestinal parasites. In recent years, the use of these drugs has increased, which has already resulted in environmental contamination and possible negative effects on biota, and increasing attention has been paid to the technology of removing such harmful substances from the environment. In this work, the efficiency of removing selected pharmaceuticals (albendazole, febantel, and mebendazole) and mixture of febantel and mebendazole by commercial reverse osmotic (RO) and nanofiltration (NF) membranes from solutions in demineralized water was investigated. The test was performed using 6 different RO/NF membranes: XLE, LFC3, NF90, KH, NF270 and HL. The highest separation efficiency was shown by RO LFC3 membrane, although other membranes also showed very high efficiency. The dominant mechanism of separation of pharmaceuticals is size exclusion, and in addition there are other influences such as electrochemical effect and physicochemical interactions between membranes and pharmaceuticals. The existence of interactions between membranes and pharmaceuticals was proved by FTIR analysis of the tested membranes before treatment and after treatment with a model solution of pharmaceuticals.