The analysis of ¹³⁷Cs accumulation by plants of forest, marsh, meadow, psamophytic, and ruderal communities in the Dnipro River floodplain (Ukraine) was carried out. It was established that plants of psammophytic and ruderal habitats are characterized by insignificant ¹³⁷Cs pollution (from 334 to 16.2 Bq/kg) and a low radionuclide accumulation coefficient (from 0.04 to 0.82). This primarily concerns such species as Berteroa incana (L.) DC., Calamagrostis epigejos (L.) Roth, Tanacetum vulgare L., Echium vulgare L., Oenothera biennis L., Artemisia absinthium L., Verbascum lychnitis L., Melilotus albus Medik., Helichrysum arenarium (L.) Moench, Cichorium intybus L., Achillea millefolium L., Hypericum perforatum L., and Thymus serpyllum L. In the plant samples taken from the meadow and the swamp ecosystems, the ¹³⁷Cs content did not exceed the permissible level (370 Bq/kg). Exceeding the normative indicator for ¹³⁷Cs was detected in the forest ecosystem plant samples. Among such economically valuable plant species are Chelidonium majus L., Convallaria majalis L., Quercus robur L., Rubus idaeus L., and Calluna vulgaris (L.) Hill. In addition, the ¹³⁷Cs accumulation coefficient of certain perennial species of mossy, herbaceous, and dwarf shrub layers (Pleurozium schreberi (Willd. ex Brid.) Mitt., Convallaria majalis, and Calluna vulgaris) exceeds this value for the woody plant species. The intensity of radionuclide uptake by plants is determined both by the biological characteristics of the species and by the soil and the cenotic habitat conditions. The species specificity of radiocesium accumulation by plants of specific biotopes and the direct dependence of the plant accumulation coefficient on the density of biotope contamination with radionuclides were confirmed. The conducted studies illustrated not only interspecies differences in the intensity of 137Cs accumulation in one type of local habitat, but also variations in the accumulation of radionuclides in different systematic groups and life forms.