Urban park ecosystems are an integral part of the natural environment and form a mosaic of habitats resulting from the diversity of soil cover for the growth of plants with different ecological requirements.  The study was conducted in six urban parks in the Upper Silesia region (Poland) and investigated the chemical properties, the content of heavy metals (HM) in the soils and on the underground (UP) and aboveground parts (AP) of Chelidonium majus as an essential medicinal plant. Soil samples were taken directly beneath the Ch. majus clumps in the root occurrence zone, the average thickness of which was about 12-15 cm. The reaction of soil can be described as slightly acidic (5.3±0.2-6.7±0.1 in KCl) to alkaline (7.1±0.1-7.5±0.3 in H₂O). Organic carbon (OC) content at all sites was high, ranging from 3.6±0.4 to 12.5±0.76%, with the highest total nitrogen (Nt) content of 0.66±0.01%. The average content of total phosphorus (Pt) in all samples is 549 mg kg^-1 (and its range: 303±4.7-955±10.5 mg kg^-1), indicating its anthropogenic origin. The concentrations of HM in the topsoil and plant samples are varied. The highest contents of Zn (1363±1.6 mg kg^-1), Pb (527±0.8 mg kg^-1) and Cd (13.6±0.3 mg kg^-1) in the soil were confirmed in 3 locations and exceeded the permissible standards. Environmental indicators, such as the geo-accumulation index, the enrichment factor, and the potential ecological risk index, showed that the analysed soils are strongly contaminated with HM. In plant material, the highest concentrations of HM were found in UP and AP, respectively. Zn showed the highest values among the elements tested in soil and plant tissues. Pb and Cd generally dominated in the underground parts, while As, Hg and Cr dominated in the aerial parts. The identification of HM levels in the plant-soil system will provide valuable information on the behaviour of HM which is important in the context of the sustainable development of urbanized areas.