The application of pesticides and chemical fertilizers constitutes a potential risk to human and animals due to the presence of their residues in the food. Thiacloprid belongs to a group of neonicotinoid insecticides. It shows a cytotoxic/cytostatic effect in human peripheral blood lymphocytes probably due to DNA damage. The use of thiacloprid is increasingly widespread worldwide, therefore is very important the assessment of its possible genotoxic and cytotoxic effects on a living organism. That is the reason why we studied the thiacloprid influence on the structure and stability of DNA in presented work. We have been studied the thiacloprid interaction with calf thymus DNA. Association constant was determined by fluorescence spectroscopy using equilibrium receptor-ligand binding analysis. The thermal denaturation of DNA was used to identify the mode of interaction. Viscosity changes were recorded to confirm/disconfirm the intercalation mode of interaction. Given the results, we can conclude that neonicotinoid pesticide thiacloprid destabilizes DNA. It changes the structure and stability of DNA through binding into the minor groove by hydrophobic or hydrogen interactions.