Specific recognition and detoxification for copper is the key step for the early diagnosis and treatment of various diseases such as neurodegenerative disease and Wilson's disease. Herein, a Chlorella vulgaris-inspired versatile theranostic nanoparticles is facilely and greenly prepared by assembling quercetin into poly(beta-cyclodextrin) (PQNPs), which is further employed in the specific recognition and detoxification for Cu2+ in vitro and in vivo. PQNPs can be used in the detection of Cu2+ in aqueous solutions with fast response time (<5 s) and low detection limit (6.499 nM). The detection for Cu2+ in water and serum can be achieved by naked eye instantaneously on a PQNPs-based paper sensor, and PQNPs can also act as a biological diagnostic agent for the Cu2+ imaging. Remarkably, PQNPs significantly enhance cell viability of the cell models induced by Cu2+ through the synergistic capacities of chelating Cu2+ and antioxidation. The detoxification of PQNPs for copper poisoning model is further ascertained in vivo, and it found that poly-β-cyclodextrin is capable of crossing the blood–brain barrier. Taken together, the as-prepared versatile theranostic nanoparticles possess advantages of simple composition, significant theranostic efficacy, and novel treatment pattern, presenting an intriguing avenue to develop therapeutics for tackling abnormal copper metabolism in the clinic.