The Ivorian hitman only took three shots on target during the match, but found the net with every one as Pal Dardai’s side moved into fourth place in the German top flight.
The victory was the capital club’s third away game in a row, and Dardai’s counterattacking style is clearly suited to Berlin’s attacking options, and particularly Kalou, who boasts the movement and finishing ability to profit on the break.
The former Blues frontman man opened the scoring on 33 minutes as he finished past former Manchester United stopper Ron-Robert Zieler, before doubling his lead early in the second period.
Cristiano Ronaldo: Chelsea & Man United braced for £70m PSG mega bid
Ronaldo opens door to Real Madrid exit; Manchester United & PSG on alert
Chelsea gossip: Terry backs Mourinho as legend eyes shock return
While a Hiroshi Kiyotake penalty halved the deficit for the home side, a Kalou penalty re-established a two-goal cushion to take Hertha fourth.
Kalou spent six years at Stamford Bridge, winning the Premier League in 2010, four FA Cups and the Champions League in 2012.