Herein, the chlorophyllin effect on the binding of proflavine, doxorubicin, ethidium bromide, and berberine to the DNA was studied by the spectrophotometry technique. For the titration data analysis, the multivariate curve resolution-alternating least squares method (MCR-ALS) was used. The pure spectra of all the absorbing particles in the systems and their concentration profiles were obtained. It was shown that chlorophyllin forms complexes with all the studied ligands. The equilibrium parameters of the ligand interactions with chlorophyllin and the DNA in the binary (ligand-chlorophyllin and ligand-DNA) and ternary (ligand-chlorophyllin-DNA) systems were obtained. It was found that in the presence of chlorophyllin, the number of ligand molecules bound to the DNA decreases. The main reason for this effect is heteroassociation since the calculated values of the constants for the interactions of the ligand with the DNA and chlorophyllin are similar. A comparison of the theoretical isotherms of ligands binding to the DNA in the ternary systems with ones obtained directly from the decomposition data was performed to test the presence of other mechanisms of the chlorophyllin competitive action. It is shown that taking into account only the heteroassociation of ligands is enough when describing the experimental isotherms. The protector action of chlorophyllin is not realized in the studied ternary systems; consequently, chlorophyllin does not interact with the DNA.