The former Barcelona and Bayer Leverkusen defender has penned a deal with the Partenopei that will run until 2017
The Brazilian centre-back has previously played in Europe for Bayer Leverkusen and Racing Santander - for whom he featured on loan from Barcelona.
Henrique spent four years under contract at Camp Nou, although he was farmed out to other clubs for the duration of that time before rejoining Palmeiras permanently in 2012.
However, now the 27-year-old has now returned to Europe with the Partenopei.
"Napoli can announce the official signing of Henrique from Palmeiras, who has signed a contract until June 30, 2017," the Italian club stated on their official Twitter account.
Partenopei president Aurelio De Laurentiis also praised the defensive recruit, tweeting: "Welcome Henrique! Your experience and your quality will integrate perfectly with our great team."
Napoli are also reportedly hoping to sign Saint-Etienne left-back Faouzi Ghoulam before the close of the January transfer window.