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Fungi play significant roles in the geochemical processes of heavy metals in the environment. However, the interaction between heavy metals and fungi, especially at the cellular level, is quite complicated and remains unknown. This study explored the mutual interaction mechanism between Pb 2+ and Trichoderma viride by combining batch experiments, spectroscopy, and in vitro approaches. Batch experiments revealed that Pb 2+ had toxic effect on T. viride, originally causing the biomass of T. viride decreased from 1.3 g in the control group to 0 g in the presence of 200 mg/L Pb 2+ . The difference in biomass further led to varied pH, even decreasing from 5.7 at the outset to 3.4 due to the acid-production properties of T. viride. Moreover, structural deformation and damage of T. viride mycelium appeared when exposed to Pb 2+ , and were more evident at a higher dose of Pb 2+ exposure. The growth curve exhibited that T. viride gradually adapted to Pb 2+ exposure, which related to Pb 2+ exposure concentration. Further, intracellular and extracellular secretions of T. viride changed with varying exposure concentrations of Pb 2+ , indicating that T. viride adapted differently to different concentrations of Pb 2+ , and MT participated in the detoxification of T. viride. SEM-EDX showed that T. viride could bio-adsorb and bioaccumulate more Pb 2+ when exposed to more Pb 2+ , which was closely related to the content of P. And carbonyl, phosphate, and amino groups of T. viride participated in the Pb 2+ biosorption onto T. viride, as evidenced by FT-IR and XPS. Meanwhile, the biomineralization and reduction of Pb 2+ by T. viride were observed by XRD and XPS, which might be a possible factor for Pb 2+ biosorption and bioaccumulation. CLSM showed that the bio-adsorbed and bioaccumulated Pb 2+ were mainly distributed in the membrane of T. viride mycelium., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)