The development of a novel near-infrared (NIR) probe for the detection of toxic Hg2+ in organisms with high selectivity and sensitivity is of great interest but remains a great challenge. Hence, in this work, a new NIR fluorescence enhanced sensor (TBBA), which contains a D-A structure as the NIR fluorophore and rhodanine-3-acetic acid as the receptor, has been developed for the detection of Hg2+ with high selectivity, sensitivity, low limit of detection (13.10 nM) and good binding constant (2.37 × 104 M-1). The mechanism of TBBA response to Hg2+ was further proved by 1H NMR titration, HRMS, and theoretical calculations. Furthermore, TBBA is applied as a fluorescent probe for imaging living cells and zebrafish, indicating that it can be potentially applied for Hg2+ sensing in both environmental and biology fields.