A large area of the Chernobyl Exclusion Zone was affected by severe wildfires in April 2020. This dataset presents the results of a study conducted following the fire in September/October 2020 to measure the migration of 137Cs and 90Sr in soils collected from three study sites located within forested areas on the left bank of the Pripyat River within the Chornobyl Exclusion Zone. Data comprise activity concentrations of 90Sr and 137Cs measured in soil samples. Soils were sampled layer-by-layer (0-10 cm, 10-20 cm, 20-30 cm, 40-50 cm, 50-60 cm, 60-70 cm, 70-80 cm, 80-90 cm, and 90-100 cm) from three locations at each of the three study sites. At each of the three study sites, circular plots were established on September 21st 2020 and soil samples collected; the circular plots were of different sizes dependent upon tree density. On October 8th 2020 a tripod was installed at the centre of each study site; the plot coordinates were noted and information on the trees present recorded (diameter, height and condition (dead or alive)). The dataset comprises two files. These files contain information on site and sampling locations, date of sampling, Cs-137 and Sr-90 activity concentration ((Bq kg-1) and analysis uncertainty (2-sigma)) in soil samples taken at 10cm intervals to a depth of 1 m, tree condition after wildfire (measured October 8th 2020); tree diameter (measured at a height of 1.3 m above ground level) and tree height (m).