The J-aggregation of anionic cyanine dye, 5,5’ – disulfopropyl-3,3’ – dichloro - thiacyanine sodium salt (TC) in the presence of 2x10-3 M KCl and citrate capped silver nanoparticles (AgNPs, diameter ~10nm) was investigated. The influence of added salt (KCl), as well as AgNPs and TC concentration on the intensity of the absorption bands with the maxima at 464 and 481 nm, characteristic of the J-aggregation of the dye in solution and on AgNPs surface, respectively, was studied. The spectrophotometric and fluorescence spectra confirmed that AgNPs induced the decomposition of J-aggregates formed in solution on the account of their formation on NPs surface. The obtained results enabled the evaluation of number of TC molecules per AgNPs participating in J-aggregate formation. The experimental results yielded about 320 molecules of TC per AgNPs in at least three layers in a slanted orientation.