The 31-year-old forward's existing deal was due to expire at the end of the current campaign, but the terms of his new contract remain undisclosed.
"We're delighted that Salomon has decided to stay with us, in spite of other offers," said Hertha sporting director Michael Preetz. "He's a cornerstone of this team and will continue to help our development."
Kalou, who joined Hertha from OSC Lille in summer 2014 added, "I'm really happy in Berlin and still have a lot to achieve with Hertha. I want to help build on the progress the team has made in recent years."
The Ivorian, a UEFA Champions League winner with former club Chelsea FC, has scored 26 goals in 75 Bundesliga appearances to date.
Watch: Salomon Kalou on Hertha's chances of qualifying for Europe: