Arsenic that adversely affects human health is frequently reported in certain regions in India and other parts of the world. A low cost, portable, and eco-friendly field test system is required to monitor the levels of arsenic in drinking water procured from different tube wells and open wells. This paper presents the construction of biosensor strain by transforming E. coliDH 5α with the plasmid pJSKV51 carrying in-frame promoter operator region as well as entire arsR gene, part of arsD gene and enhanced green fluorescent protein (EGFP) gene. This strain was able to induce EGFP in presence of arsenic III ion. This paper further presents a novel EGFP-based bio-electronic sensing methodology to develop a low-cost battery operated system to measure the fluorescence emitted by biosensor strain and display the numerical values of the concentrations of arsenic in water samples. In this method, a blue light of 480 nm excites the EGFP to produce a green fluorescence signal in proportion to arsenic concentration. The developed device includes a compact embedded system to measure the signal fluorescence using light sensor, programmable controllers and liquid crystal display to show the corresponding concentration of the arsenic in ppb. The experimental results show that the system can detect and display over a range from 5 to 100 ppb. © 2001-2012 IEEE.