Sustainable recycling and safe disposal of waste polyethylene terephthalate (PET) are growing concerns worldwide. We have synthesized green fluorescent carbon nanodots (CDs) utilizing waste PET bottles as carbon precursors following a greener solvothermal synthetic route in this work. The obtained CDs (∼6 nm) exhibited excellent photoluminescence properties and displayed high selectivity for lead ions (Pb²⁺) through a fluorescence quenching effect. Besides, the CDs possessed a highly negative zeta potential value of −40 mV, which suggests good colloidal stability of the nanosuspension. The synthesized optical nanosensor demonstrated excellent anti-interference activity for Pb²⁺ detection despite the presence of co-existing cations or anions. The calculated low detection limit of ∼21 nM and fast response time of the synthesized nanoprobe displayed its significant potential in trace level detection of Pb²⁺ ions from the aqueous medium. Furthermore, the synthesized CDs proved their excellent practicality in sensing Pb²⁺ ions from actual water samples. Therefore, the present work's findings illustrate the CDs as a promising fluorogenic probe for environmentally benign and cost-effective detection of Pb²⁺ ions from aqueous solutions.