[8] In October, Watson travelled to Pune in India to compete at the 2008 Commonwealth Youth Games where she won the gold medal, winning the final against Kyra Shroff.

[14] She played her semifinal on the same day and was victorious against Daria Gavrilova to reach the final, where she faced doubles partner Yana Buchina.

[16] At the 2009 French Open, Watson and her partner, as the third seeds, reached the girls' doubles final where she and Tímea Babos faced the second-seeded pair of Noppawan Lertcheewakarn and Elena Bogdan and were beaten in a match tie-break.

She went on to qualify for the next tournament she entered and again faced Smith in the semifinals; however, this time Watson was victorious and went on to beat Anna Fitzpatrick in the final to win her first title.

[23] At the Eastbourne International, Watson qualified for the main draw by defeating Anna Smith, Tsvetana Pironkova and Bojana Jovanovski.

[29] Partnering Patrick Ogier, Watson also reached the quarterfinals of the mixed doubles, where they were defeated by the third seeds Sarah Borwell and Ken Skupski, representing England.

She continued her winning streak in the main tournament and beat ninth seed Carla Suárez Navarro to get into the quarterfinals,[31] where she lost to Peng Shuai.

[40] Watson continued her good form entering the grass-court season when she beat 15th seed Chanelle Scheepers in the first round of the Birmingham Classic.

[54] She won the doubles competition of the Stanford Classic, where she played with Marina Erakovic to beat Vania King and Jarmila Gajdošová in a second set tiebreak.

[55] She received an ITF wildcard into the singles tournament at the London Olympics, where she defeated Sílvia Soler Espinosa,[56] before losing her second-round match to Maria Kirilenko.

She also played in the women's doubles in the Olympic tournament with Laura Robson, losing in the first round to Angelique Kerber and Sabine Lisicki.

[62] Watson made a WTA Tour singles final for the first time in her career at the HP Open where she beat Polona Hercog, sixth seed Anabel Medina Garrigues, Pauline Parmentier and Misaki Doi.

Her first game back after recovering was at the French Open, where she lost to Stefanie Vögele in three sets, saying after the match she knew it would be tough but that she was very disappointed.

[75] Beginning the grass-court season, she entered the Birmingham Classic seeded 14th and defeated Melinda Czink in the first round,[76] her first victory since returning from her illness before she lost to qualifier Alla Kudryavtseva.

She claimed a two-set victory, before defeating sixth seed Anna Karolína Schmiedlová (who had played most of her semifinal the day before) in the final.

Over the course of the rest of the season, her best result was a quarterfinal showing at the Hong Kong Open where she lost to former major champion Samantha Stosur.

[111] On grass courts, Watson's second-round appearance at the Birmingham Classic with a win over Camila Giorgi resulted in her re-entry into the world's top 50.

[112] At Wimbledon, she won the mixed doubles title with Henri Kontinen, defeating Robert Farah and Anna-Lena Grönefeld in the final.

[115] Starting the year at the Hopman Cup partnered with Daniel Evans, the duo were knocked out in the group stages, between them winning only one of nine matches.

[117] Watson was runner-up at the ITF event of Surbiton[118] and reached Eastbourne semifinals, defeating top-10 player Dominika Cibulková in the second round,[119] Anastasia Pavlyuchenkova in the third[120] and Barbora Strýcová in the quarterfinals,[121] before falling to Caroline Wozniacki.

[124] A first round defeat at the Prague Open in April to Anna Karolína Schmiedlová was Watson's eighth consecutive loss on the WTA Tour.

[125] She finally snapped her losing streak when she defeated Kateryna Bondarenko in the first round of the Nuremberg Cup at the end of May to record her first win in four months.

Watson was docked a point for swearing as she and Tatjana Maria lost to Katerina Siniaková and Barbora Krejčíková in the doubles quarterfinals in Wimbledon.

She defeated CoCo Vandeweghe, Kateryna Bondarenko, Christina McHale and Wang Xiyu to reach the final, where she overcame qualifier Leylah Fernandez in three sets, clinching the match on her tenth championship point.

[149] At the Miami Open, Watson broke a six-year losing streak at the event when she defeated Arantxa Rus in the first round where after a 3-hour 25 minute battle.

[154] In her 12th attempt, Watson finally reached the fourth round at Wimbledon defeating Kaja Juvan,[155] before she lost to Jule Niemeier.

[156] At the close of the season she helped the Great Britain team reach the semifinals of the 2022 Billie Jean King Cup[157] At the 2023 Australian Open, she went out in the first round of qualifying.

[158] She reached her first WTA Tour quarterfinal in almost two years at Hua Hin with wins over second seed Yulia Putintseva[159] and Han Na-lae.

[180] At the Billie Jean King Cup finals in November, Watson and Olivia Nicholls lost to Viktória Hrunčáková and Tereza Mihalikova in the decivisve doubles match as Great Britain were eliminated in the semifinals by Slovakia.

[185] According to Nigel Sears, head of women's coaching at the Lawn Tennis Association, Watson possesses "a complete game",[186] with variety including a consistent one-handed backhand slice, volleys and angles.