"First match of a tournament there are nerves from everyone so first game to break settled us both down and allowed us to relax and play our game," Venus said.
Venus did save two break points on serve in the sixth game of the first set from 15-40, serving two second serve aces. But he and Klaasen broke again in the 9th game to take the set 6-3 in 40 minutes.
Games went with serve until the sixth game of the second set when Venus and Klaasen broke again for 4-2. Venus served out the match to start the defence of his title in the best possible way.
"We took care of the net really well and made the other guys play some tough shots out there so we took care of that but the next team will be tough and have confidence from their first round win so we will just start again," Venus said.
Venus and Klaasen will next face another French pair, the experienced Jonathan Eysseric and Hugo Nys for a place in the third round tomorrow night.
Venus will be back on court tonight however for his opening mixed doubles match. He and Taipei's Hao-Ching Chan are the 6th seeds and take on Dutch players Demi Schuurs and Matwe Middelkoop in the first round.
Meanwhile Erin Routliffe has been beaten in the first round at the ITF Futures tournament in Hua Hin in Thailand.
The 23-year-old has lost a tight match to fifth seeded American Jacqueline Cako who has a WTA ranking of 277. The match lasted 2 hours 25 with Cako winning 6-3, 4-6, 6-4.