This study investigates the utilization of carbon dots (CDs) from neem leaves (Azadirachta indica) decorated onto cadmium sulfide (CdS) for the photocatalytic degradation of ciprofloxacin. A comparative study of ciprofloxacin degradation with pristine CdS and CD decorated CdS demonstrated high degradation of ∼ 75 % with CD/CdS when compared to bare CdS (∼68 %). Process optimization studies were further carried out with CD/CdS catalysts at different solution pH (4–10), feed concentrations (10–50 mg/L), catalyst loadings (25–125 mg/L), temperatures (10 – 30 °C), and lamp power (25, 50, 250 W and sunlight). Higher temperatures, combined with a solution pH of 7 and catalyst loading of 100 mg/L favored the enhanced degradation of 20 mg/L of ciprofloxacin. The ciprofloxacin degradation rate increased linearly with temperature with an apparent activation energy of 27 kJ mol−1. The CD/CdS photocatalyst demonstrated maximum degradation rates with higher lamp powers while it also showed remarkable performance under natural sunlight achieving the same degradation within 3 h.