The interaction of double strand calf thymus DNA (dsDNA) with the antibiotic, Ciprofloxacin (Cf) has been investigated using differential pulse voltammetry, impedance spectroscopy, UV–Vis spectroscopy, spectroelectrochemistry and atomic force microscopy (AFM) measurements. Investigation revealed good interaction between Cf and dsDNA, with formation constant of 2.65 × 104 M−1. Electrochemical measurements established the mechanism of interaction to be the intercalative in nature, which has been supported by the spectroscopic findings. The zeta potential analysis reveals that the Cf-dsDNA complex is stable enough to remain in the solution and is stabilized through electrostatic interaction as well as the intercalative binding. The AFM images of dsDNA (at 47 μM concentration) with various concentrations of Cf (0.1, 0.2, 0.5, 1, 5, 10 mM) reveal the condensation of DNA in the presence of the antibiotic drug. The mechanism of the dsDNA condensation by the presence of Cf is ascertained to be through the electrostatic interaction between the –NH– group of Cf and the phosphate group of DNA and also through the carboxylic acid group of Cf with the amine groups of the nucleotides present in the DNA strands.