Migliacci studied in Florence where his family had settled, here he entered in a competition for young players, in which he won a stay of three days to Cinecittà and a modest role in a film by Nino Taranto.

After this, he moved to Rome and the world of cinema where he worked in small parts in about 18 films.

In 1958, with Domenico Modugno, Migliacci co-authored the song "Nel blu, dipinto di blu", also known as "Volare", which has become one of the most well-known Italian songs in the world.

Afterward, he worked in drama series for television and several radio plays.

He was then the illustrator for The Pioneer children's magazine directed by Gianni Rodari.