The playmaker's previous deal had been due to expire at the end of the month, but he has now committed his future to the Italian champions until June 2016.
Pirlo moved to Juve from Milan in May 2011, and is an integral part of the team who have won three consecutive Scudettos.
A statement on Juve's official website said "the fantastic story of Andrea Pirlo and Juventus continues", and the 35-year-old now looks set to end his playing career in Turin.
Pirlo has made 131 appearances for Juve, scoring 14 goals.
He is currently away in Brazil with the Italian national team for their FIFA World Cup campaign, which begins against England on Saturday.
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