The 27-year-old Portuguese defender had reportedly attracted the interest of Harry Redknapp, who had been keen to bring the Porto star to west London.
However, after completing a medical at Castelvolturno, he opted instead to help Walter Mazzarri's men in their fight for the Scudetto title by signing a six-month loan deal.
He told the club's official website: "I'm really happy to wear this shirt. I wanted to join Napoli because it's a big club with a lot of great players.
"I've heard a lot about the passionate fans and I can't wait to experience a game at the Stadio San Paolo."
After joining Porto from Belenenses in 2008, Rolando played a key role as the Dragons won three Portuguese championships in four years and claimed the Europa League trophy in 2011.
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