The Ivorian forward got on the end of a Fernando Torres cross to give the Blues the edge going into the second leg of their Champions League quarter-final at Stamford Bridge
Kalou struck in the second half, meeting a Fernando Torres cross to give the Blues the lead and the advantage of an away goal as the tie heads back to Stamford Bridge next month.
"It's a good result, the away goal is very important," Kalou told Sky Sports.
"It was a good game, everyone worked hard and when you do that as a team it makes it easier to win.
"Everyone worked hard today. We deserved to win the game and I wasn't worried about the late chances. We are ahead by one goal and we have to get ready for the next game now."
The Ivorian has found his first-team opportunities limited this season but returned to the starting line-up due to Chelsea's busy schedule of late.
"You want to play every game but the manager makes the decisions and you have to respect that," Kalou said.
"He gave me my chance to play and prove myself on the pitch and I'm happy to play and give everything I can."
Didier Drogba had been caught on camera appearing to feign fear at drawing Benfica following their victory over Napoli in the previous round but midfielder John Obi Mikel added that Chelsea's performance proved the seriousness with which they had approached the fixture.
"We know what a good side they are," Mikel insisted.
"Coming here, we knew it was going to be very difficult. We put in a hard shift, kept defending and hoped we could get a chance [to score] and that's exactly what we did.
"This result means a lot for us. Coming here, we knew if we could get a win or a draw that would allow us to go back home and seal the tie.
"Getting a victory is fantastic and we just have to keep going and hopefully we can get a good result at home and go through."
Mikel also backed Roberto Di Matteo's decision to make changes for the Benfica clash following their draw against Tottenham on Saturday.
"Whatever decisions the manager makes, we just have to get on with it," the Nigerian added.
"He's the manager, he decides who plays and I think everyone on this team is very happy.
"The guys on the bench you could see coming to the pitch – they all know how important this game is for us."