He started acting at the age of 6, on the stage of his school in Birigüi, São Paulo. He graduated with a degree in law from the Pontifical Catholic University of São Paulo (PUC-SP) in 1997, but he never practiced it.

His dream of becoming actor was delayed by his modeling career. He was a successful model for eight years of which two were overseas, with a house in Paris, but all the while he was traveling to such cities as New York, London, Berlin, and Milan. He was unhappy, though, and decided to resume his pursuit of an acting career.

In 2001, he had his first significant regular role in the soap opera, Laços de Família. He played the role of "Edu", a doctor who got involved with a woman many years older than he was - played by actress Vera Fischer.

In 2002, Gianecchini was chosen to be the exclusive top model for Armani in Brazil, a position he apparently still holds to this date (Maria Fernanda Candido, his co-star in Esperança, is the female equivalent for Armani).

Since August 2011, Gianecchini has been battling against cancer (angioimmunoblastic T-cell lymphoma) and has undergone chemotherapy treatment.[