In 2002, sports brand Yonex offered to sponsor Nehwal’s kit. As her status and rankings improved, the number of sponsorships also increased. In 2004, Bharat Petroleum signed the rising star. She is one of the athletes supported by Olympic Gold Quest. She endorses Commune Builder, Edelweiss Group, Emami, Fortune Cooking Oil, Godrej No Marks, Herbalife Nutrition, Huawei Honor smartphone. Indian Overseas Bank, Iodex, NECC, Sahara Group, Star Sports, Top Ramen Noodles, Vaseline and Yonex.

Few months after she entered the International Badminton Circuit, a 17 year old Nehwal participated at the World Championships where she lost to Jiang Yanjiao of China. In 2006, Nehwal became the under-19 national champion and created history by winning the “Asian Satellite Badminton tournament” (India Chapter) twice, becoming the first player to do so. In May 2006, at age 16, she became the first Indian woman and the youngest player from Asia to win a 4-star tournament – the Philippines Open. Entering the tournament as the 86th seed, she went on to stun several top seeded players including the then world number two Xu Huaiwen before defeating Julia Wong Pei Xian of Malaysia for the title. The same year Nehwal reached the final of 2006 BWF World Junior Championships where she lost a hard-fought match against top seed Chinese Wang Yihan. She also competed at the 2006 Doha Asian Games.

The BWF Superseries, launched on 14 December 2006 and implemented in 2007, is a series of elite badminton tournaments, sanctioned by the Badminton World Federation (BWF). BWF Superseries has two levels: Superseries and Superseries Premier. A season of Superseries features twelve tournaments around the world, introduced in 2011, with successful players invited to the Superseries Finals held at the year’s end.

In 2007 At a very young age of 17, Nehwal went on to take part at the All England, where she challenged experienced Wang Chen in the Round 2, but went down in 3 games 21–17, 13–21, 16–21. She represented India at the Sudirman Cup in Scotland in 2007. At the 2007 BWF World Championships, she won her opening matches against Jeanine Cicognini of Switzerland and 13th seed Juliane Schenk of Germany, but lost the next round to French Pi Hongyan with score 13–21, 17–21. She was the finalist at the Indian International challenge in 2007 where she lost to Kanako Yonekura in 2 games.

Two years after losing the final to Wang Yihan, she became first Indian to win World Junior Badminton Championships by defeating ninth seeded Japanese Sayaka Sato 21–9, 21–18. She participated in the 2008 Beijing Olympics where she was unseeded. She began her fight with a win against Russian Ella Diehl (2–0) in Round 1 & Ukrainian Larisa Griga (2–0) in 2nd round. She became the first Indian woman to reach the quarter finals when she upset reigning Asian Games champion no. four seed Wang Chen of Hong Kong in a three-game thriller. In the quarter-finals Nehwal lost a 3-gamer to world number 16 Maria Kristin Yulianti. Nehwal was leading 11–3 in the decider but couldn’t hold on against her opponent and lost the match with 28–26, 14–21, 15–21 scoreline.

In September 2008, she won the Chinese Taipei Open 2008 beating Lydia Cheah Li Ya of Malaysia 21–8, 21–19. She was also a semifinalist at the China Masters Superseries after she beat reigning World Champion Zhu Lin in quarterfinals. Nehwal was named “The Most Promising Player” by the Badminton World Federtion in 2008. She qualified for the season ending Superseries Finals which consists of most consistent players of the year. She defeated Pi Hongyan and Wong Mew Choo in early rounds. She lost to Tine Baun in Round 3. She entered semifinals but lost to Wang Chen with scores 21–15, 14–21, 16–21.

In August 2009, she reached to the quarterfinals of the World Championships, losing to the second seed Wang Lin. She qualified for the season ending Superseries Finals in December, where she lost the opening match to Wong Mew Choo (Eventual Champion) but won the next two group matches against Porntip Buranaprasertsuk & Canada’s Charmaine Reid. She again reached the semifinals of this tournament but went down, this time to Germany’s Juliane Schenk. She won India Grand Prix tournament later in the year, defeating compatriot Aditi Mutatkar in the final with scores 21–17, 21–13.

Nehwal won the 2010 India Open Grand Prix Gold, beating Wong Mew Choo of Malaysia in the final and thus justifying her billing as top seed in the tournament. Nehwal, again seeded no.1, won the Singapore Open Super Series 2010, by beating qualifier Tai Tzu-Ying of Chinese Taipei in the final of the Singapore Open 21–18, 21–15 having defeated World Champion Lu Lan earlier in the semifinal. Nehwal reached a career high of world no. 3 in the women’s singles badminton world rankings on 24 June 2010.

She defended her Indonesia Open title in three tough games against Sayaka Sato, 21–19, 13–21, 21–11. This was her third super series title and her third successive title following wins at Indian open & Singapore Super series. On 15 July 2010, with 64791.26 points, Nehwal reached a career high world ranking of No. 2 only behind Wang Yihan of China. 2nd seed Nehwal, a tournament favourite, crashed out of the 2010 BWF World Championships in Paris after losing to 4th ranked Chinese Wang Shixian in straight sets 8–21, 14–21.

As on 27 September 2010, Nehwal dropped to No. 7 ranking after giving a miss to 2010 China Masters Super Series and 2010 Japan Super Series due to her preparation for the 2010 Commonwealth Games. Top seed Nehwal won the gold medal in the Women’s Singles badminton event in the 2010 Commonwealth Games held in New Delhi. after beating Wong Mew Choo of Malaysia 19–21, 23–21, 21–13. After her win Nehwal said, “when I was a match-point down, it was like a shock. It was a big match and winning it means a lot to me. Even many years from now, those present here will always remember how Saina won the gold. It is a proud feeling”. Nehwal confirmed her participation for the 2010 Hong Kong Super Series after a gap of more than five months since her win in the 2010 Indonesia Super Series in June 2010. On 12 December 2010, she defeated Wang Shixian 15–21, 21–16, 21–17 in the final of the 2010 Hong Kong Super Series to win her fourth career Super Series title.

2nd seeded Nehwal beat Sung Ji-hyun of South Korea 21–13, 21–14 to win the Swiss Open title. Nehwal faltered after a good start as she lost to the then world number three Wang Xin of China in the finals to finish runner-up in the 2011 Malaysian Open tournament. She was a part of Indian Team in the 2011 BWF Double Star Sudirman Cup mixed team who managed to reach the quarterfinals of this elite mixed team event for the first time ever, as India managed to beat Thailand 3–2, even when Nehwal lost her tie against Ratchanok Intanon. In the quarterfinals against China, Nehwal put up her best performance and beat the then world number two Wang Xin with 21–15, 21–11, but still the Chinese managed to move into the semi finals with a 3–1 win over India.

Nehwal successfully defended her Swiss Open Title by defeating Wang Shixian 21–19, 21–16 on 18 March 2012, a day after she turned 22 years old. On 10 June 2012, she defeated Thailand’s Ratchanok Intanon 19–21, 21–15, 21–10, to lift the Thailand Open title. On 17 June 2012, Nehwal won the 3rd consecutive Indonesia Open by defeating Li Xuerui, a player who was on 30 match winning streak with most dominant performance in the season so far with scores 13–21, 22–20, 21–19.

At the London Olympics, Nehwal was seeded 4th in the Draw. In the Group stage she defeated Swiss Sabrina Jaquet (2–0) & Belgian Lianne Tan both in straight games. She reached the knockout phase where she defeated Dutch Yao Jie with scores 21–14, 21–16. She then faced Tine Baun, the no. 5 seed whom she defeated with 21–15, 22–20 scoreline. She afterwards advanced to semifinals where she lost to top seed Wang Yihan in two straight games 13–21, 13–21. On 4 August 2012, she won the bronze medal when Wang Xin retired from the match after an injury at 18–21, 0–1.

On 21 October 2012, she won the Denmark Open after defeating Germany’s Juliane Schenk. Nehwal successfully entered the finals of French Open, but she lost against Minatsu Mitani in straight sets. She participated at the season ending Superseries Finals. In the group stage, she lost to Tine Baun (1–2), won against Juliane Schenk (2–0) & lost the 3rd match to Ratchanok Intanon (0–2). She reached the semifinals but lost a well contested match to Li Xuerui of 3 games, 20–22, 21–7, 13–21.

Nehwal signed an endorsement deal worth Rs. 400 million with the popular sports management firm Rhiti Sports in 2012. However, she severed this deal in 2013 and signed up with KWAN entertainment and marketing solutions for an undisclosed sum. She has a dedicated sporting range with the multinational sports goods manufacturer Yonex, 4% of the profits of which goes to her.

Her autobiography, Playing to Win: My Life On and Off Court, was released in 2012.

On 26 January 2014 Nehwal defeated World Championship bronze medalist P.V. Sindhu 21–14, 21–17 to win the 2014 India Open Grand Prix Gold Tournament. In the final of 2014 Australian Super Series on 29 June 2014, Nehwal defeated Spain’s Carolina Marin 21–18, 21–11 to win the title. She withdrew from 2014 Commonwealth Games due to fitness Issue & injury problems she carried during Australian Open. She lost in the quarterfinals of World Championships again, this time to Li Xuerui. She was the quarter-finalist at the Asian Games as well, where she lost to Wang Yihan. She became the first Indian player to win the China Open by beating Japan’s Akane Yamaguchi 21–12, 22–20 in the final. She contested at the Superseries Finals and won all of her group matches against top seed Wang Shixian (2–0), Bae Yeon-ju (2–1) & Sung Ji-hyun (2–0). She reached the semifinals once more, but lost to eventual champion Tai Tzu-ying with scores 21–11, 13–21, 9–21.

Defending champion Nehwal won the Syed Modi International by defeating Carolina Marín in the final. She became the first Indian woman shuttler to reach the finals of the All England, but lost to Marín in the final. On 29 March 2015, Nehwal won her maiden women’s singles title at the India Open, by beating Ratchanok Intanon. This assured her of becoming World number 1 when the latest BWF rankings were released on 2 April. With this, she became the first Indian player to achieve this feat in Women’s category.

Nehwal dealt with injuries in early 2016 but she eventually recovered. She reached the semifinals of the Badminton Asia Championships after defeating the third seed Wang Shixian but settled for bronze medal, after losing to Wang Yihan 16–21, 14–21. At the Australian Super Series, Nehwal went into the finals after beating Ratchanok Intanon in quarters & Wang Yihan in semifinals. She defeated China’s Sun Yu in the final by 11–21, 21–14, 21–19.

The BWF World Tour, announced on 19 March 2017 and implemented in 2018, is a series of elite badminton tournaments, sanctioned by Badminton World Federation (BWF). The BWF World Tour is divided into six levels: World Tour Finals, Super 1000, Super 750, Super 500, Super 300 (part of the HSBC World Tour), and the BWF Tour Super 100.

She married fellow badminton player, Parupalli Kashyap in a private ceremony on 14 December 2018.

At 2018 Denmark Open, Nehwal was unseeded. She defeated Hongkonger Cheung Ngan Yi scoring 20–22, 21–17, 24–22 in her favour. She then defeated 2 tough Japanese opponents in successive rounds; beating Akane Yamaguchi & Nozomi Okuhara. After an easy win against Indonesia’s Gregoria Mariska Tunjung in semifinal, she met her arch-rival and the no.1 seed Tai Tzu-ying. In the past 16 meetings Tai had won 11 and Nehwal wanted to break that jinx but couldn’t managed and went down by 13−21, 21−13, 6−21. Nehwal went into the finals of Syed Modi Badminton Super 300 tournament but lost to Han Yue of China.

As of 2018, a biopic titled Saina and directed by Amol Gupte is being made on her, with actress Parineeti Chopra playing the title role.

Nehwal joined the Bharatiya Janata Party in Delhi on 29 January 2020 in the presence of party’s national general secretary Arun Singh. Her sister Abu Chandranshu Nehwal also joined the party. She was quoted as saying “Narendra Modi is working hard for the country, and has always inspired me.”