The veteran from Blainville, Que., battled to a 7-5, 7-6 (7-5) victory over Daniela Hantuchova of Slovakia in first-round play Tuesday night at the US$2.168 million hardcourt event at Uniprix Stadium.
Wozniak, ranked 55th to Hantuchova's 35th, broke service for a 6-5 second-set lead, but let three match points slip away to take it to a tiebreaker. Then a light rain wet the court just enough to force a 55-minute delay.
They returned to mostly empty seats as most of the centre court crowd went home, but even without as much hometown support she held on to take the tiebreak.
"I tried to finish it when I had the match points, but it wasn't easy," Wozniak told the crowd in a courtside interview. "I gave everything on every point.
"It was important for me to win here."
Wozniak, who has not advanced beyond the second round in nine previous Rogers Cups, will next face former world No. 1 Jelena Jankovic. The Serb is 4-0 in her career against Wozniak, once in 2008 in Montreal.
There was a big high and a crashing low for Stephanie Dubois of Laval, Que., who wasted a chance to upset 41st-ranked Chanelle Scheepers but ended up dropping a 1-6, 6-3, 6-0 decision.
Dubois breezed through the first set, breaking service three times, but then could no longer hold her own serve, losing it seven straight times against the South African. It was less of case of serving badly than of failing to put away easy points.
"It's disappointing that in the second set I didn't get the momentum and keep on going," said 25-year-old Dubois, currently ranked 151st. "I started to make mistakes.
"I didn't finish points well today. I did in the first set, but not after."
Scheepers advanced to a second-round meeting with 14th-seeded Flavia Pennetta.
The 25-year-old Dubois beat Scheepers in their own previous meeting in a lower level tournament in 2008.
She was among three Canadians who got wild card entries into the draw along with Wozniak and Wimbledon junior champion Eugenie Bouchard, who opens play Wednesday against Shahar Peer.
The 16 seeded players have a bye to the second round, including top-seeded Victoria Azarenka.
Azarenka arrived directly from the London Olympics, where she won bronze in singles and then took gold in mixed doubles with Belarus compatriot Max Mirnyi.
Only a few weeks earlier on the same court, she had reached the semifinals of Wimbledon, where she lost to Serena Williams.
"It's not easy to regroup mentally because you want to celebrate a bit, but you have no time," Azarenka said. "You have to go back to the tennis court and practice.
"But I'm happy to be here. I can't wait to start this tournament and just play tennis again."
Azarenka, the top seed, will open against Austrian Tamira Paszek, who won her first match 6-2, 6-1 over Julia Goerges of Germany.
Two qualifiers opened with victories as Sesil Karatantcheva of Kazakhstan, who turns 22 on Wednesday, blanked Sorana Cirstea of Romania 6-0, 6-0 and Jana Cepelova of Slovakia beat Sweden's Sofia Arvidsson 6-3, 6-3. Cepelova's next test is against eighth-seeded Italian Sara Errani.
Roberta Vinci of Italy overcame deficits of 4-1 and 5-2 in the third set deficit to defeat Yarina Wickmayer of Belgium 6-2, 3-6, 7-5, while Carla Suarez Navarro topped Maria Jose Martinez Sanchez 1-6, 6-4, 6-3 in an all-Spanish matchup.
Simona Halep downed Michelle Larcher de Brito 6-4, 6-3 and next will play 4th-seeded Samantha Stosur.
Azarenka is hanging onto the No. 1 world ranking by a thread and will have to hold off second seeded Agnieszka Radwanska and No. 3 Maria Sharapova to stay on top. Sharapova can regain the top ranking if she wins the tournament, while Radwanska would need to win and have both Azarenka and Sharapova bow out before the quarter-finals.
"It's really exciting," said Azarenka, who got her first grand slam title this year at the Australian Open. "We're all showing consistent tennis through the year.
"We're all winning tournaments. It's exciting for people to watch when it's close and we're doing our best competing against each other. It's definitely going to be interesting by the end of the year."
The hardcourt tournament began a day later than usual and will end on Monday night to accommodate the London Olympics.