[5] Her biggest junior achievement was at the 2009 French Open girls' singles, where she beat Daria Gavrilova of Russia in two sets in the final.

[12] Mladenovic turned professional in 2009, making her Grand Slam debut at that year's Australian Open where she received a wildcard but was defeated by 14th seed Patty Schnyder.

[14][15] At the Internationaux de Strasbourg, Mladenovic won her first match on the WTA Tour, coming back from 2–5 in the final set to win the tiebreak against Stefanie Vögele.

Mladenovic partnered up with Daniel Nestor to reach the semifinals of the mixed doubles, where they were defeated by the seventh-seeded team of Max Mirnyi and Andrea Hlaváčková in a close three-setter.

She advanced to the third round with a victory over Danka Kovinić but lost to Alison Van Uytvanck in straight sets while fighting for a spot in the last 16.

Mladenovic won the doubles event partnering Caroline Garcia, beating Ekaterina Makarova and Elena Vesnina in the final.

[31] In June, Mladenovic reached her second WTA Tour singles final at the Rosmalen Grass Court Championships in which she lost to CoCo Vandeweghe.

[11] In doubles, Mladenovic (partnered with Garcia) reached the final, where the French team was defeated by Bethanie Mattek-Sands and Lucie Šafářová.

During the WTA Finals, the French women defeated Julia Görges and Karolína Plíšková in the quarterfinals, but fell to Mattek-Sands and Šafářová in the semifinals.

During the 2016 Fed Cup final between France and the Czech Republic, Mladenovic lost the first rubber narrowly against Karolína Plíšková 3–6, 6–4, 14–16, a match that lasted 3 hours 48 minutes.

She later played doubles with Garcia in the fifth and decisive rubber against Plíšková and Barbora Strýcová, which they lost 5–7, 5–7, enabling the Czechs to win the Fed Cup for the fifth time in six years.

However, in doubles, reunited with partner Caroline Garcia, she reached the semifinals of the event, where they lost to Andrea Hlaváčková and Peng Shuai.

[39] At the St. Petersburg Ladies' Trophy, Mladenovic won her first round match against Elise Mertens before upsetting reigning Australian Open finalist Venus Williams to reach the quarterfinals.

In the semifinals, the French woman defeated rising player Natalia Vikhlyantseva to reach the first WTA Premier singles final of her career.

Mladenovic's good form continued at the Mexican Open, where she stormed past Varvara Lepchenko before winning a marathon match against Heather Watson to reach the quarterfinals, in which she defeated Kirsten Flipkens.

[43] Though she did end up losing to Lesia Tsurenko in the final, her success in February allowed Mladenovic to reach a career-high WTA singles ranking of No.

She also had success with Kuznetsova in the doubles, knocking out the fifth-seeded pair of Andrea Hlaváčková and Peng Shuai in the second round before losing in the quarterfinals.

Against German wildcard Laura Siegemund (who was playing in her hometown), Mladenovic led 4–1 in the final set tiebreak but ended losing the match 1–6, 6–2, 6–7.

14, reached her first career Premier Mandatory singles final at the Madrid Open by defeating her doubles partner Svetlana Kuznetsova in the semifinals.

At her home Grand Slam, the French Open, she won her first-round match in a tight three sets against American Jennifer Brady.

She defeated the fourth seed and defending champion Garbiñe Muguruza in three sets to advance to her second quarterfinal of a Grand Slam tournament in her career.

[55] Mladenovic started her season at the Brisbane International, where she lost in the first round to the eventual singles finalist Aliaksandra Sasnovich in three sets.

In her next tournament, the Sydney International, she retired in second set of her first-round match against the Australian wildcard Ellen Perez due to heat stress.

[56] At the Australian Open, Mladenovic's poor form in singles continued, losing her first round match in straight sets to world No.

[63] In the Indian Wells doubles event, Mladenovic partnered Babos and they lost in the semifinals to Ekaterina Makarova and Elena Vesnina.

[65] Mladenovic and Babos were the women's doubles top seeds at that tournament, losing in the quarterfinals to the unseeded Japanese pair of Eri Hozumi and Makoto Ninomiya.

[citation needed] Mladenovic lost her opening singles matches (both in straight sets) in her next two tournaments, to Tímea Babos and Victoria Azarenka in San Jose and Montreal, respectively.

[79] At the same tournament, she reached the second round in singles as a lucky loser defeating top-20 ranked Belinda Bencic to take revenge over her loss at the Madrid Open.

Partnering Zhang Shuai, she reached her third final in Flushing Meadows at the 2024 US Open defeating en route second seeds Hsieh Su-wei and Elise Mertens in the first round.

[90] Playing with Veronika Erjavec, Mladenovic won the doubles title at the 2024 WTA 125 Cali Open, defeating Tara Würth and Katarina Zavatska in the final.