Born on 23 August 1923 in Astakos, Leandros left in the 1950s for Germany to pursue a career in singing and composing.
He had some success, but shifted his focus to his daughter, Vicky, who had been singing from a very early age.
Under his pseudonym Mario Panas (Greek: Μάριο Πάνας) he was the co-composer (together with Klaus Munro) of "Après toi", the winner of the Eurovision Song Contest 1972, which Vicky performed for Luxembourg.
Leandros has composed and produced for many other artists such as Julio Iglesias, Demis Roussos, Nana Mouskouri, Ulli Martin, Freddy Quinn and Jairo, among others.
In October 2005 though, he appeared on German/Austrian TV as a surprise guest for his daughter who was celebrating her 30-year stage Jubilee.