UV–Vis spectra of camptothecin (CPT) in toluene, acetone, ethanol, acetonitrile, dimethylsulfoxide and aqueous solutions are investigated by UV–Vis spectroscopy and DFT calculations. The structures of CPT and its π-dimer have been optimized using B3LYP and B97D functionals with cc-pVDZ basis sets. Solvent effects were estimated using the Integral Equation Formalism Polarizable Continuum Model. Electron transitions in the studied systems were evaluated by TD-DFT treatment. Whereas the strong peak at the highest wavelength corresponds to the CPT monomer, the existence of the blue shifted one may be explained by its π-dimers formation instead of CPT hydrogen bonding with water molecules.