Radiocaesium and radiostrontium contamination in the ‘soil – rhizosphere – plants (aerial parts)’ system was monitored in the floodplain ecosystem of the Yenisei River in the near impact zone of the Krasnoyarsk Mining and Chemical Combine (MCC). The monitored system included soil, rhizosphere, and sedge vegetation on islands and the river’s east bank. The 137Cs and 90Sr specific activities displayed intricate space and time patterns controlled by the river water level, including the time and duration of floods and their correlation with the sedge vegetation season. The specific activities of both radionuclides, especially 137Cs, were above the background in all years of observation, except in a few cases. The soil-to-plant transfer factor (TF) patterns showed continuous 137Cs and 90Sr influx into the system and annual variations in the shares of their bioavailable and fixed forms, especially for 90Sr. The 90Sr distribution in the ‘soil – rhizosphere – plants’ system observed in 2014–2016 provides evidence for possible local fallout.