Abstract A novel fluorescence quenching immunochromatographic sensor (ICS) was developed for detecting chromium (Cr3+) within 15min utilizing the fluorescence quenching function of gold nanoparticles (Au-NPs). The sensor performed with a positive readout. When the low concentrations of Cr3+ samples were applied, detection signals of the test line (T line) were quenched, whereas when higher concentration Cr3+ samples (1.56ng/mL) were applied, the detection signal of the T line appeared. The detection signal intensity of the T line increased with increasing concentrations of Cr3+. The low detection limit of developed fluorescence quenching ICS was 1.56ng/mL. The fluorescence quenching ICS has a linear range of detection of Cr3+ comprising between 6.25ng/mL to 800ng/mL. The recoveries of the fluorescence quenching ICS to detect Cr3+ in tap water ranged from 94.7% to 101.7%. This result indicated that the developed sensor gave higher sensitivity and reliable reproducibility. It could provide a general detection method for small analyte in water samples.