This paper presents a simple, sensitive and reliable strategy for the colorimetric determination of coralyne (COR) using citrate-capped silver nanoparticles (Cit-AgNPs). In the presence of NaC1, COR induces the aggregation of Cit-AgNPs, resulting in a change of color from shinny yellow to pink. Significant variables affecting the proposed method (salt concentration, interaction time, interaction temperature and pH) were evaluated and optimized to achieve the maximum sensing performance. Optimal conditions were obtained with 500 mu M NaCl, at ambient temperature, pH = 7.0 and within 5 min of COR addition onto Cit-AgNPs. The ratio of UV-vis absorbance at 612 nm to 400 nm (A(612)/A(400)) linearly responded to the concentration of COR from 26 to 404 nM with a detection limit of 8.54 nM under the optimized conditions. The proposed method was found to be highly selective toward COR compared to several other small molecules which are typical intercalating ligands, anticancer agents or heterocyclic compounds with similar molecular structure to COR. It also exhibited satisfactory selectivity in the presence of a wide range of organic and inorganic interfering substances. Finally, the applicability of the method for the detection of COR in real samples (human urine and tap water) was confirmed.