Rare earth elements (REE) are important resources, but REE in the environment are also deemed to be a new class of pollutant. Phytoremediation, using the hyperaccumulator Dicranopteris pedata, offers a promising approach for reclaiming and recycling REE from mining tailings. However, how in situ leaching affects the topsoil characteristics of mining areas and the absorption of REE by D. pedata remains elusive. To address these issues, an in situ leached hill and an un-leached hill were selected for comparison. This study revealed the following: (1) a significant increase in total REE, heavy REE (HREE), and available REE at the leached hill by 47.28%, 100.74%, and 108%, respectively; (2) a marked elevation in the contents of REE in D. pedata of the leached hill, especially HREE in rhizomes, stems, and foliage by 634.45%, 232.63%, and 156.8%, respectively; and (3) a Pearson correlation analysis indicating that the enhanced uptake of REE by D. pedata at the leached hill is related to available REE in the topsoil. This study illuminates the mining-induced dynamics of soil REE migration and plant uptake, reinforcing the feasibility of phytoremediation for REE tailings.