A green and effective strategy to prepare a novel lotus root-like three-dimensional (3D) bismuth/biomass derived activated carbon (Bi@BAC) composite was developed for simultaneous electrochemical sensing of Pb2+ and Cd2+. The BAC supports herein were prepared from naturally-abundant Platanus seeds chemically activation by KOH, with dense and uniform bismuth micro/nano-sized particles successfully anchored on the carbon substrate through microwave-assisted hydrothermal treatment and subsequent carbothermal reduction process. Simultaneous electrochemical detection of Pb2+ and Cd2+ using square wave anodic stripping voltammetry (SWASV) was performed with the novel composite modified carbon paste electrode (CPE). Under optimized experimental conditions, the Bi@BAC/CPE demonstrated good linear response for both two target metal ions in the concentration range of 0.5 to 50 μg L-1, with limits of detection (LOD, S/N = 3) of 0.13 and 0.08 μg L-1 for Pb2+ and Cd2+, respectively. Moreover, the modified electrode displayed high resistance to interference, long-term stability and good reproducibility. The Bi@BAC/CPE also demonstrated satisfactory recovery level for the detection of target metal ions in real water samples.