Excessive use and inadequate management of plastic have led to environmental pollution with plastic nanoparticles (PNP). Although the number of studies on the adverse effects of PNP is increasing, there is a lack of reliable information on the effects of PNP on human health, especially their interactions with the endocrine system. In addition to PNP, the environment is also polluted with numerous drugs. Paracetamol, ibuprofen, carbamazepine and fluoxetine are among the drugs that are quantified in the environment in significant quantities. PNP can adsorb drugs and form complex mixtures whose action has not been investigated. Despite this, the presence of environmental pollutants in complex mixtures is neglected and the primary focus is on the effect of individual substances. The aim of the research was to determine endocrine disrupting effects of complex mixtures of PNP and drugs. Research is based on the examination of the effects on the estrogen receptor (ER) acitivity and the process of steroidogenesis. Complex mixtures were prepared by mixing drugs and/or nanoparticles of polystyrene, polypropylene and polyethylene. PNPs are characterized by means of shape, size, size distribution and ζ potential. The effects of individual substances and their mixtures on cell survival were tested using the MTS assay and flow cytometry. PNP uptake into cells was determined by flow cytometry. The effects on ER activation were tested with the luciferase assay and OECD Guideline No. 455, and the influence on the steroidogenesis with qPCR and the LC-MS/MS method and OECD Guideline No. 456. The obtained results showed that the effects of individual substances differ significantly compared to the effects of complex mixtures. Mixtures of PNP and drugs showed significantly stronger toxic and endocrine disrupting effects. Binary and ternary mixtures of drugs show a complex dose-biological response relationship that depends on the composition of the mixture.