The interaction between ketoconazole (KTZ) and Herring Sperm DNA (HsDNA) have been studied by cyclic voltammetry, differential pulse voltammetry, UV-vis absorption and fluorescence spectral studies and viscometric methods. The measurements were performed in 0.1 mol L-1 PBS buffer solution at pH = 7.4. The voltammetric behaviour of KTZ in the presence and absence of HsDNA was investigated at glassy carbon electrode using Cyclic Voltammetry and Differential Pulse Voltammetry. The calculated binding quenching constants (KSV) were 1.057 x 104, 5.9268 ×103, and 3.039 ×103 L mol-1 at 298, 303 and 308 K respectively. The Stern-Volmer quenching rate constant (kq), binding site number (n) and corresponding thermodynamic parameters (ΔH, ΔG and ΔS) were calculated.