Thymol exhibits a range of biological effects, which can be highly beneficial in the local treatment of skin diseases. However, due to the possible cytotoxic effects of thymol on skin cells, its topical dermal application may be limited. This study aimed to examine the biocompatibility of thymol in vitro on the HaCaT cell line, after being incorporated into phospholipid formulations: vesicular phospholipid gels (VPGs) and liposomes of analogous phospholipid composition. VPGs were prepared by high-pressure homogenization, while liposomal formulations were produced by the film method, followed by homogenization through extrusion using polycarbonate membranes. The VPGs exhibited an average vesicle diameter ranging from 140 to 151 nm (polydispersity index < 0.27), while the extruded liposomes were slightly larger (144 - 164 nm) with a polydispersity index < 0.12. The zeta potential of the VPGs ranged from -2.1 to -3.8 mV, compared to the liposomes with zeta potential ranging from -19.4 to -21.7 mV. The presence of cholesterol in the formulations resulted in a modest increase in the average vesicle diameter and polydispersity index, as well as slightly more negative zeta potential compared to the formulations without cholesterol. The biocompatibility of the formulations containing thymol was tested in vitro on the HaCaT cell line using the MTT assay 24 hours after treating the cells. The results confirmed the cytotoxic potential of free thymol at concentrations  125 μg/ml. Additionally, the results demonstrate that the cytotoxic effects of thymol are eliminated when incorporated into the phospholipid formulations, as the tested formulations containing thymol were biocompatible with HaCaT cells across the entire range of tested concentrations (7.82 – 4000 μg/ml).