Born in Pisa, Guido Cappello moved to Gorizia at a young age, then in the 1960s to Milan.
In 1960 he won the Italian Chess Championship in Perugia, ahead to Alberto Giustolisi, Federico Norcia and Enrico Paoli.
Guido Cappello was awarded the title of National Chess Master in the same year.
In the 1963 Italian Chess Championship in Imperia he still touched the title, ranking on equal points with the winner Ennio Contedini, who prevailed by technical play-off.
Guido Cappello has had several successes in International Chess Tournaments, ranked 3rd in Savona (1967) and in Milan (1968).