The 26-year-old has been linked with moves the likes of Liverpool and Manchester United in recent season.
The new deal will keep Hamsik at the Stadio San Paolo until the summer of 2018.
"I have just renewed my contract with Napoli until 2018 and I'm very happy," Hamsik told Mediaset Premium.
"I do not decide who we sign in the transfer market, but Skrtel's definitely a great player and would suit Napoli. Higuain? I think it will be a great year for him."
"Itís a perfect marriage with Hamsik," Napoli president Aurelio De Laurentiis wrote on Twitter. "He is a great man, a great professional and a great player who honours the Napoli jersey.
"It is a shirt he is happy and satisfied to honour. We have renewed his contract, extending it to 2018."