Using the bioaccessible concentration to which plant roots and microorganisms are exposed may provide a better estimation for toxicity than using total concentration. Bioaccessibility of REEs in highly organic soil were measured using Diffusive Gradient in Thin Films (DGT) and partial extractions with CaCl2. The correlation of DGT accumulation to other bioaccessible determining methods and plant roots were weak. Modifications to the DGT SOP such as increasing deployment time and resupplying the labile pool to the DGT surface improved these relations. To some extent, DGT mimics the action of plants if plant uptake is limited by diffusion. Therefore, DGT is capable of serving as a predictor of plant uptake and availability of the rare earth metals. This is the first study that demonstrates the suitability of measuring REEs with DGT in soil.