Herein, we present a novel, straightforward, eco-friendly and cost-effective method for synthesizing fluorescent carbon dots. A simple one-pot hydrothermal method was used to create blue-emitting nitrogen-doped carbon dots (N-CDs) from waste chicken feathers and ammonium chloride (NH4Cl) as precursors. The research demonstrates that N-CDs not only exhibit excellent photostability, but also serve as a versatile nanoscale fluorescence sensor for the efficient qualitative and quantitative detection of chlortetracycline (CTC) in samples. The mechanism of fluorescence quenching is attributed to the specific and rapid quenching of N-CDs fluorescence by chlortetracycline through the static quenching and inner filter effect (IFE). The concentration of CTC within the range of 0.05–0.35 mM exhibits a significant linear relationship with the fluorescence quenching of NCDs, as indicated by the formula (I0-I)/I = 4.74248c(CTC)-0.09041. Subsequent spiked recovery experiment confirms the feasibility of this method for the detection of CTC in samples. Therefore, leveraging the concept of turning waste into treasure, this study successfully developed a green and cost-effective method for synthesizing NCDs from natural biomass, offering a novel perspective for further development of multifunctional sensors.