The second-seeded Sharapova, who received a bye into the second round, handled Thai veteran Tamarine Tanasugarn 6-2, 7-5 on the hardcourts at Ariake Colosseum. The former world No. 1 from Russia is now 5-0 lifetime against the 34-year-old Tanasugarn.
"I served really well today," Sharapova said. "It was important for me to serve well because she reads the ball really well. I had a bit of letdown in the second set. She started playing really well. I was glad I was able to come back and win it in two sets."
The three-time Grand Slam champion Sharapova titled here back in 2005 and 2009.
In some other second-round action, seventh-seeded French star Marion Bartoli held off Japan's Ayumi Morita 6-3, 0-6, 6-3 and eighth-seeded former world No. 1 Jelena Jankovic handled Czech Barbora Zahlavova Strycova 6-4, 6-2. The Serbian Jankovic was the '09 runner-up here to Sharapova.
A second-round match for ninth-seeded Pole Agnieszka Radwanska was postponed until Tuesday because of rain, and six first-round matches were suspended or postponed because of inclement weather on Day 2.
Seeded opening-round winners on Tuesday were No. 12 Ana Ivanovic and No. 13 Julia Goerges. The former No. 1 Ivanovic drilled Aussie qualifier Anastasia Rodionova 6-4, 6-0, while the German Goerges grounded France's Pauline Parmentier 6-3, 6-4. The Serbian Ivanovic was the Tokyo runner-up in 2007.
Additional first-round wins came for American Vania King, Russian Maria Kirilenko, Aussie Jarmila Gajdosova, Luxembourg's Mandy Minella and Czech Klara Zakopalova. King whipped Chinese Zhang Shuai 6-1, 6-0, while the qualifier Minella, who will tangle with Wimbledon champ Petra Kvitova in her next outing, doused 40-year-old Japanese crowd favorite Kimiko Date-Krumm 1-6, 6-3, 6-3. The 2005 Pan Pacific champion Date-Krumm will turn 41 on Wednesday.
Gajdosova will face world No. 1 and defending Pan Pacific titlist Caroline Wozniacki in the round of 32. Wozniacki beat since-retired Russian star Elena Dementieva in last year's finale here. Kirilenko will battle sixth-seeded U.S. Open champ Samantha Stosur in the third round.
The 2011 Pan Pacific champ will collect $360,000.