A goal in each half of the encounter was enough for the Old Lady to edge Heiko Herrlich’s side as they claimed their first victory in 2018.
Valentino Lazaro broke the deadlock for the visitors after connecting to Vladimir Darida’s through pass with two minutes left before the end of the first half.
After the restart, Kalou took advantage of Jonathan Tah’s blunder to double Hertha’s lead with a cool finish in the 58th minute.
The 32-year-old forward has now scored nine goals in 20 league matches this campaign. He was replaced by Mathew Leckie in the 80th minute.
Hertha Berlin are placed 11th in the Bundesliga log with 30 points from 22 games – six points adrift of a Uefa Champions League spot.
The Old Lady host Mainz 05 for their next league encounter on February 16.