Alongside Oleksandra Korashvili from Ukraine, she also reached the final of the Australian Open, falling one match shy of completing the calendar-year Grand Slam.

[11] In March 2021, Krejčíková made progress to her first singles final of a WTA 1000 tournament at the Dubai Championships, eventually losing to Garbiñe Muguruza.

In doubles, she had more success, reaching the semifinals at the Diamond Games, debuting in the main draw of the French Open, and winning her first title at the Tournoi de Québec.

[30] Krejčíková won her first Grand Slam tournament mixed doubles title at the Australian Open, playing with Rajeev Ram and defeating wildcard entrants Astra Sharma and John-Patrick Smith in the final.

For the first time in her career, she qualified for the main draw of the Australian Open, beating Kaia Kanepi before losing to Ekaterina Alexandrova in the second round.

[47][48] In the Middle East swing, Krejčíková's most notable result in doubles was making the Doha semifinals with Siniaková, before losing to Jeļena Ostapenko and Monica Niculescu.

They then defeated Bethanie Mattek-Sands and Iga Świątek in straight sets to claim their second French Open title,[61][62] and the first singles/doubles sweep in Paris since Mary Pierce in 2000.

She began with straight-sets wins over Astra Sharma,[72] Christina McHale,[73] Kamilla Rakhimova[74] and ninth seed Garbiñe Muguruza to reach her maiden US Open quarterfinal.

[citation needed] Krejčíková represented the Czech Republic in the inaugural 2020–21 Billie Jean King Cup Finals in Prague in November.

However, the long season appeared to catch up with her as she lost both of her singles rubbers to Angelique Kerber of Germany and Bencic of Switzerland, and did not play the doubles.

Originally scheduled to participate in Indian Wells as the top seed, she pulled out due to the ongoing arm injury that flared up just before the start of the tournament.

This injury also kept Krejčíková out of the Miami Open, and forced her to withdraw from all four clay-court tournaments she had signed up for in Stuttgart, Madrid, Rome, and Strasbourg, the latter at which she was the defending champion.

Having not played a match in three months due to an elbow injury, Krejčíková entered the French Open singles draw as the second seed and defending champion.

[84][85] Krejcikova's grass court season did not start well with an early loss to Marta Kostyuk at the 2022 Eastbourne International in singles and winning just one match in doubles where she partnered Ena Shibahara.

[86] At the same tournament in doubles, she reached the final with her partner Siniakova and won the title for a second time defeating top seeds Elise Mertens and Zhang Shuai in straight sets.

However, she was more successful in doubles, where she won the title with Siniaková, coming back from a set down to defeat Taylor Townsend and Caty McNally in the final.

[88][89] Krejcikova returned to the singles court at the inaugural 2022 Tallinn Open and got first ever wins against her first four opponents: Ajla Tomljanović, Marta Kostyuk, Beatriz Haddad Maia and Belinda Bencic, four players she had never beaten before.

[106] After a difficult return from injury where she suffered several early losses, Krejčíková won her 7th career singles title, the San Diego Open, defeating Sofia Kenin in the final.

In November, she represented the Czech Republic in the 2023 Billie Jean King Cup finals in Seville, winning one singles and two doubles matches alongside Siniakova.

[111] Krejcikova began 2024 with a run to the quarterfinal at the Australian Open, recording wins over wildcard entrant Mai Hontama,[112] Tamara Korpach,[113] qualifier Storm Hunter[114] and Mirra Andreeva.

[119] Krejcikova returned to the tour at the Porsche Grand Prix in Stuttgart, Germany, after more than two months away but lost in the first round of the singles to Veronika Kudermetova.

[121] In May, Krejcikova and Siegemund were finalists at the WTA 1000 event, the Madrid Open, where they lost to Cristina Bucsa and Sara Sorribes Tormo in the final in straight sets.

[128] Seeded 31st, she reached her second Grand Slam tournament singles final at Wimbledon, defeating Veronika Kudermetova,[129] qualifier Katie Volynets[130] and Jéssica Bouzas Maneiro[131] in the first three rounds.

[140] Krejčíková reunited with Kateřina Siniaková in the doubles at the Prague Open, winning their first title together on home soil by defeating wildcards Bethanie Mattek-Sands and Lucie Šafářová in the final as they warmed up for the 2024 Summer Olympics.

[141][142] At the Olympic Games in Paris she lost in the quarterfinals of the singles to Anna Karolína Schmiedlová,[143] while her and Siniaková also fell in the last eight in the doubles to Mirra Andreeva and Diana Shnaider.

Having received a bye into the second round at the Ningbo Open, she defeated lucky loser Ma Yexin,[148].but retired due to a back injury while trailing in her quarterfinal against Mirra Andreeva.

As a result, she is capable of generating and redirecting power both crosscourt and down-the-line with both her groundstrokes, allowing her to hit winners, or induce unforced errors from opponents, with a high degree of accuracy.

[158] Although Krejčíkova typically plays at the baseline until the opportunity arises to attack the net, she occasionally utilises the serve-and-volley tactic to surprise opponents, and win points easily.

In the post-match press conference, Krejcikova revealed this was a talent she developed as a junior when the deep lobs would bounce over her shorter opponents’ heads and over the fence!

[160] Despite her aggressive playing style, Krejčíkova possesses excellent movement, speed, stamina, footwork, and court coverage, allowing her to defend to an exceptionally high standard, and she is an effective counterpuncher, extending rallies until she creates the opportunity to hit a winner.