In 2014, she won her first main-draw match on the WTA Tour at the Swedish Open in Båstad, defeating Yaroslava Shvedova in the first round.

In Wimbledon, she reached her first Grand Slam main draw after exiting ten times in the qualification rounds.

[5] In April, she made an upset by reaching the final as a qualifier in Stuttgart, losing to compatriot and defending champion Angelique Kerber.

On her way to this success she beat three top-10 players in a row (Simona Halep, Roberta Vinci and Agnieszka Radwańska), all of them in straight sets.

In September, she won her first Grand Slam title, winning the US Open mixed-doubles championship with Mate Pavić.

[8] After winning only one of nine matches on hardcourt, Siegemund started the clay-court season by reaching the semifinals of the Charleston Open.

She won her second career title in her hometown Premier event Stuttgart Open after a wildcard entry, defeating Kristina Mladenovic in the final, in three sets.

[10] Siegemund made her return to the WTA Tour in April at the Charleston Open where she lost in the second round to tenth seed Naomi Osaka.

[20] Playing for Germany in the Fed Cup tie against Brazil, Siegemund won both of her rubbers beating Teliana Pereira and Gabriela Cé.

[21] Coming through qualifying at the Qatar Open, she made it to the second round where she lost to top seed Ashleigh Barty.

[23][24] Siegemund returned to action in August at the Palermo Ladies Open where she was eliminated in the second round by fourth seed and eventual finalist, Anett Kontaveit.

18 and tenth seed Marketa Vondrousova before losing to fellow qualifier and doubles partner Vera Zvonareva.

Siegemund began season at the first edition of the Abu Dhabi Open where she lost in the first round to Kirsten Flipkens.

[30] At the Australian Open, Siegemund was eliminated from the tournament in the first round by tenth seed and seven-time champion, Serena Williams.

[32] Getting past qualifying at the Qatar Ladies Open, Siegemund made it to the second round where she lost to eighth seed and two-time champion, Victoria Azarenka.

[34] At Miami, she withdrew from her second-round match against 14th seed and three-time champion, Victoria Azarenka, due to a right knee injury.

[35] Starting her clay-court season at the Stuttgart Open, Siegemund was eliminated in the second round by top seed and eventual champion, Ashleigh Barty.

[41] Seeded eighth at the first edition of the Bad Homburg Open, Siegemund's first grass-court tournament of the season, she reached the quarterfinals in which she was defeated by eventual finalist Kateřina Siniaková.

[43] Representing Germany at the Summer Olympics, Siegemund fell in the first round to fourth seed and eventual bronze medalist, Elina Svitolina.

[51] Playing with Beatriz Haddad Maia, she reached her second WTA 1000 final at the Indian Wells Open, losing to top seeds Barbora Krejčíková and Kateřina Siniaková.

[52] In July, she reached her first WTA Tour singles final in over six years at the Poland Open, but lost to world No.

[54] Following her Jiangxi Open doubles title, she reached the top 10 for the first time in her career and also qualified with Vera Zvonareva for the WTA Finals in Cancun.

In the final, they beat the Polish team of Iga Świątek and Hubert Hurkacz in a match tie-break to claim the title.

[60] In doubles with Barbora Krejcikova, she reached the quarterfinals but lost also to Storm Hunter and her new partner Katerina Siniakova.

Siegemund and Krejcikova were runners-up at the Madrid Open in May, losing 0–6, 2–6 to Cristina Bucsa and Sara Sorribes Tormo in the final of the clay-court WTA 1000 event.

[61] At the French Open, she won her third Grand Slam title by winning the mixed doubles with Édouard Roger-Vasselin.

[70] Siegemund and Shibahara were runners-up at the Pan Pacific Open, losing to Shuko Aoyama and Eri Hozumi in the final.

[71] Partnering with Beatriz Haddad Maia, Siegemund was runner-up in the doubles at the Adelaide International, losing to Guo Hanyu and Alexandra Panova in the final.