Thiolated poly(m-phenylenediamine) (PmPD), overoxidized in NaOH solution, was used in combination with in situ plated Bi film electrode for simultaneous and sensitive analysis of Cd2+ and Pb2+ by square wave anodic stripping voltammetry (SWASV). Thiolation of PmPD was achieved during the electropolymerization of m-phenylenediamine, and the introduced S atoms improved the preconcentration efficiency of the PmPD for Cd2+ and Pb2+; and overoxidation altered the surface structure of the polymer, which endowed more active area for the nucleation of Bi. Due to the synergetic effect of thiolation, overoxidation and Bi film, the prepared PmPD modified Bi film exhibited excellent performances in the simultaneous analysis of Cd2+ and Pb2+, showing a linear range from 6 to 240 mu g L-1 for Cd2+ and Pb2+. The detection limits were 0.02 mu g L-1 for Cd2+ and 0.04 mu g L-1 for Pb2+, respectively. This approach opens a new avenue to monitor trace heavy metal ions precisely and rapidly. (C) 2015 The Electrochemical Society. All rights reserved.