A novel Schiff base and its Pb²⁺-complex have been synthesised and exploited as colorimetric and fluorescent–colorimetric sensors respectively targeting the detection of arginine (Arg). Both the chemo-sensors employed here are simple, easy to synthesize and cost effective. They exhibit excellent selectivity and sensitivity towards Arg by giving dual responsive signals of visible colour change and ‘on–off’ fluorescence change within 1 min. The chemo-sensors having sufficiently low detection limits and rapid response times warrant their application in environmental analyses of Arg.