20 Leo is a spectroscopic triple system composed of 3 very similar stars, one of which seems to be a δ Sct star. Observations at high spectral and high time resolution have been obtained at the Observatoire de Haute Provence with the ELODIE spectrograph on the 1.9-m telescope. The spectra were taken during 7 nights in 2003 January and cover the whole optical domain from 3900 to 6800 Å. We used a Fourier transform technique recently developed by P. Hadrava to disentangle the combined spectrum. Application of the method allows the derivation of radial velocities at all orbital phases (even at phases of complete blending), as well as individual spectra for each component. From these computations we deduced more accurate individual radial velocities and improved orbital parameters describing the motion of the inner binary. Model atmospheres were used to analyze each individual spectrum and determine stellar fundamental parameters of the three components such as effective temperature, surface gravity and projected rotation velocity.