A simple, cost-effective, and convenient bimodal strategy for the detection of toxic flavonoid rutin was proposed. The strategy depends on fluorometric and electrochemical determination of rutin using new type of nitrogen and sulfur co-doped carbon dots (N, S@C-dots). The fluorescence detection based on quenching the emission of N, S@C-dots by rutin through inner-filter effect (IFE), while the electrochemical detection based on direct oxidation of rutin at glassy carbon electrode (GCE) modified with N, S@C-dots. Many factors affecting fluorometric and electrochemical measurements were optimized. The decrease of emission intensity and the increase of the electrochemical signal are linear over the concentration range of 0.02−92.3 μM and 0.2−130 × 10⁻⁸ M, respectively. The limits of detections (LODs) were found to be 8.0 nM and 0.8 nM for the fluorometric and electrochemical methods, respectively. Moreover, short response times (2.0 and 2.5 min) were achieved using the fluorometric and electrochemical methods, respectively. The selectivity of the fluorometric sensor towards rutin was enhanced; in the presence of other interfering flavonoids; by the addition of bovine serum albumin (BSA).