Mercury and thallium forms a eutectic alloy that finds extensive use in thermostatic devices owing to its capability of withstanding extremely low temperature. As both these metals are highly toxic, so herein we report their co-sensing on a sensitive electrochemical platform. The performance of the designed sensing surface was tested by electrochemical impedance spectroscopy, cyclic voltammetry, square wave anodic stripping voltammetry and chronocoulometry. The fabricated electrode successfully discriminated the signals of mercuric and thallium ions in the same voltammogram without any issue of peaks overlapping. The electrode was found stable, sensitive to mercuric and thallium ions and resistant to interfering non-target metal ions at the voltammetric potential of target analytes. The role of the modifier in facilitating electron transfer between host (electrode) and guest (target metal ions) was ensured from the more intense signals at the modified electrode compared to bare glassy carbon electrode (GCE). The mediator performance of the modifier in bringing the analyte closer to the transducer was also supported by computational findings of strong interaction between the amino acid, glycine and metal ions. Under optimized conditions, the glycine modified GCE sensed mercury and thallium ions to a concentration level well below their danger limit set by the Environmental Protection Agency of USA. The cost effective, greener approach, rapid responsiveness and portable characteristics of the designed electrode suggest its practicability for the simultaneous trace level detection of thallium and mercury ions. © 2019 Elsevier Ltd