Carbon dots (CDs) samples were synthesized from orange peel waste (OPW) via a simple and eco‐friendly hydrothermal carbonization (HTC) and electrochemical (EC) bottom‐up synthesis integrated approach. The comprehensive chemical‐physical characterization of CDs samples, carried out by various techniques such as TEM, EDX, XRD, FT‐IR, underlined their morphological and microstructural features. The CDs exhibited attractive electrochemical properties, and thus an electrochemical sensor by modifying a screen printed carbon electrode (CDs/SPCE) for the detection of nitrobenzene (NB) in water was developed. Electroanalytical performances of CDs/SPCE sensor using differential pulse voltammetry (DPV) demonstrated its high sensitivity (9.36 μA μM−1 cm−2) towards NB in a wide linear dynamic range (0.1–2000 μM) and a low limit of detection (LOD=13 nM). The electrochemical sensor also shown high selectivity, long‐term stability, and repeatability. This paper might open the way to a new synergistic HTC‐EC approach for the synthesis of CDs from waste biomass material and their advanced application in highly efficient electrochemical sensors. Not just waste: An integrated approach based on linking thermal and electrochemical technologies is investigated for the valorisation of agro‐industrial waste. The obtained carbon dots (CDs) are certain of high scientific value and may add more value to industrial citrus waste. The CDs exhibited interesting physicochemical and optical properties, allowing their use as a voltammetric sensor.