An electrochemical apt sensor was designed for the ultras elective and sensitive detection of Pb²⁺ by using lead-specific binding DNA oligonucleotide as the molecular recognition element on Au nanoparticles/Nb₄C₃T_x MXene (Au@Nb₄C₃T_x) modified electrode. The Au@Nb₄C₃T_x is conjugated with thiol-modified lead-binding DNA through the Au−S bond. The DNA−Au@Nb₄C₃T_x modified glassy carbon electrode exhibited ultrahigh selectivity and enhanced response towards the detection of Pb²⁺ with a detection limit of 4 nM and linear range of 10 nM to 5 μM. This work has proved the possibility of using Nb₄C₃T_x as a robust immobilization platform for DNA oligonucleotides towards different environmental sensing and biomedical applications.