In this study, we investigated the antibacterial modification of polymers with biologically active substances in essential oils [EOs; linalool, 4-allylanisole (ALY), and trans-anethole]. These compounds were thermoplastically incorporated into a low-density polyethylene matrix via solid inert carriers [wood flour (WF) and talc and molecular sieves] with physically immobilized EOs. The concentrations of the antibacterial modifiers on the carriers and in the resulting composites were determined with three chromatographic techniques (gas chromatography with mass spectrometry, pyrolysis and gas chromatography with mass spectrometry, and high-performance liquid chromatography). The effects of such modifications to the mechanical properties of the prepared composites were studied by stress-strain analysis. Interactions on the polymer matrix carriers were observed by scanning electron microscopy.The prepared composites were also tested for antibacterial activity against both Gram-negative and Gram-positive bacterial strains. The highest efficiency of isothermal immobilization was found for systems consisting of ALY and WF. This finding was in accordance with microbiological studies. The phase of immobilizing the EOs did not influence the mechanical properties of the studied composites.