She defeated many top-10 and top-5 players, including Kim Clijsters, Martina Hingis, Amélie Mauresmo, Anastasia Myskina, Elena Dementieva, Francesca Schiavone, Jelena Janković, Agnieszka Radwańska, Marion Bartoli, and Vera Zvonareva.

It detailed a long-term affair involving Zhang Gaoli, a retired Chinese Vice Premier, who was reportedly accused of raping her.

At age 13, Peng was admitted to a hospital for heart surgery to repair a defect,[4] a situation which she explained in the 2008 "Impossible is Nothing" campaign from Adidas.

The following week, she extended her winning streak to twelve and reached the final of a $25k tournament at New Delhi before losing the championship match to Eva Birnerová.

[2] At the Australian Open, Peng won her first major singles match, defeating Maria Elena Camerin before being overcome by Venus Williams in the second round.

[5] In 2006, Peng lost her first-round ties at the Australian Open, withdrew from subsequent tournaments, and dropped out of the top 60, after losing at Indian Wells and Miami.

She reached the semifinals of the China Open and represented her country for the first time in her Fed Cup career, winning both her ties against Indonesia.

She finished the year with a 26–21 record in singles, a doubles title in Guangzhou with Yan Zi, and one top-ten win against Amélie Mauresmo.

[5] After a string of losses in 2008, Peng recorded her first win of the year at the Tier-II Bangalore Open against Anne Kremer before losing to Venus Williams;[5] she also won the doubles title with Sun Tiantian.

[7] She won the Sydney International doubles title with Hsieh Su-wei, defeating Nathalie Dechy and Casey Dellacqua in the final.

At the French Open, Peng was knocked out of the singles event but partnered with Hsieh to reach the semifinals in doubles, defeating Hantuchová & Sugiyama in the third round and the Radwańska sisters in the quarterfinals before losing to Victoria Azarenka and Elena Vesnina.

In the ITF Circuit, Peng won a trophy at the $100k event in Taipei and ended the season representing China in the 2010 Asian Games in Guangzhou.

At the Australian Open, she defeated Kateryna Bondarenko, Jelena Janković, and Ayumi Morita to reach the fourth round of a major for the first time in her career, before losing to Agnieszka Radwańska.

At the Wimbledon Championships, she defeated Sandra Zaniewska, Ayumi Morita and Arantxa Rus to reach her second consecutive round of 16 before losing to Maria Kirilenko.

She reached the final in the Brussels Open, defeating Sofia Arvidsson, Olga Govortsova, Sloane Stephens, and Romina Oprandi before losing to Kaia Kanepi.

Paired with long-time childhood friend Hsieh Su-wei, Peng clinched five double's titles in 2013, including two Premier-5 events (Rome and Cincinnati), Wimbledon,[9] and WTA Championships.

Peng and Hsieh continued their success by winning three more titles in the season, including two Premiere Mandatory events (Indian Wells and Beijing) and French Open.

At the US Open, Peng made her first Grand Slam singles quarterfinal and semifinal appearances, defeating compatriot Zheng Jie, fourth-seeded Agnieszka Radwańska, 28th-seeded Roberta Vinci, 14th-seeded Lucie Šafářová, and rising star Belinda Bencic en route, all in straight sets.

[13][14] Peng was particularly frustrated by Xu, who was constantly attacked by their opponents and making a lot of unforced errors, and decided to split the partnership.

She benefited from the withdraw from Agnieszka Radwańska in the quarterfinal and beat Danka Kovinić in the semifinal, which lasted for two days due to rain delays.

In the doubles event, Peng and Hlaváčková reached the final without dropping a set, defeating third seed and Olympic champions Makarova/Vesnina and top-seed Garcia/Mladenovic.

She won her second tour singles title at the Jiangxi International Open in Nanchan, China defeating Nao Hibino in the final.

In August 2018, Peng was banned for six months and fined $10,000 by the Tennis Integrity Unit (TIU) for coercion and offering possible financial reward so that her main partner would agree to withdraw from the ladies doubles, even after the sign-in deadline at the 2017 Wimbledon Championships.

[26] Peng lost in the second round at Guangzhou in singles but won the doubles title with Laura Siegemund, defeating Alexa Guarachi/Giuliana Olmos in the final.

[34][35][36] In February 2022, Peng announced her retirement during an interview with the French magazine L'Équipe, where she also mentioned her 2021 social media post and subsequent events.

[37][38] In November 2021, Peng reportedly accused Zhang Gaoli, a retired Vice Premier of the State Council and member of the Standing Committee of the Politburo, of sexually assaulting her in 2018.

[52][53][54] WTA chief executive Steve Simon called on Chinese authorities to investigate her allegations and stop censoring the subject, and multiple tennis personalities expressed their concerns.

[55][56] Depictions of Peng emerged via Chinese state media, but various China watchers and human rights advocates worried that they might be government propaganda and she might not be free.

[65][66] In a later video from Lianhe Zaobao and an interview with the French magazine L'Équipe, Peng said she had not accused anyone of sexual assault, but some skepticism persists, as well as debates over the meaning and legal implications of her original post.

[75] She was included in Time magazine's 100 Most Influential People of 2022, where feminist activist Lü Pin highlighted Peng's Weibo post, disappearance, and impact on the defense of women's rights against authoritarianism.