Salicylic acid is an emerging environmental contaminant, usually found at ng/L concentrations in natural waters. Its quantification usually involves liquid chromatography‐tandem mass spectrometry, which requires complex and costly instrumentation as well as time‐consuming sample pretreatment, typically involving large solvent volumes. In this work, sequential injection chromatography was exploited to develop a fast, green, cost‐effective, and highly sensitive procedure for fluorimetric determination of salicylic acid in natural waters. Analyte preconcentration directly on the chromatographic column (on‐column preconcentration) was exploited to improve detectability, yielding an enrichment factor of 122 (1.75 mL of sample) and takes only 8.5 min per determination. A detection limit of 20 ng/L, a linear response range from 0.06 to 5.00 µg/L, coefficients of variation lower than 3.0% (n = 10), and recoveries within 86 and 114% were estimated. The procedure was applied for the analyses of freshwater samples and results agreed with those obtained by liquid chromatography‐tandem mass spectrometry at the 95% confidence level. The proposed procedure encompasses in‐line concentration, isolation/separation, and detection, without the need for sample clean‐up, thus minimizing the consumption of organic solvents and risk of analyte losse.