Leander was born in Calcutta, India, on 17 June 1973 to Vece Paes, a Goan, and, Jennifer Paes, from Calcutta. He was educated at La Martiniere Calcutta, Madras Christian College Higher Secondary School and the St. Xavier’s College of the University of Calcutta. His parents were both athletes. Vece was a midfield squad member in the bronze medal-winning Indian field hockey team at the 1972 Munich Olympics although he did not personally receive a medal as he did not take to the field in any of India’s matches. His mother captained the Indian basketball team in the 1980 Asian basketball championship. Paes is a direct descendant of Bengali poet Michael Madhusudan Dutta through his mother. Paes had a live-in-relationship with Rhea Pillai in 2005. The couple have a daughter, Aiyana. She filed a case at a local metropolitan court against Paes in 2014, alleging that he had her belongings removed from a wing of his home so his visiting parents could stay there.

Paes enrolled with the Britannia Amritraj Tennis Academy in Madras (Chennai) in 1985, where he was coached by Dave O’Meara. The academy played a key role in his early development. Leander earned international fame when he won the 1990 Wimbledon Junior title and rose to no. 1 in the junior world rankings at age 17.

Paes started his Davis Cup career in 1990, when he partnered Zeeshan Ali in doubles to beat the Japanese team in a five-set encounter. His Davis cup record was 89–32 as of July 2015. He played a key role on the Indian team that reached the World Group from 1991 to 1998. He was part of the Indian team that reached the semifinals 1993 with wins against Switzerland and France, eventually losing to Australia. In singles, his major wins came against the French duo of Arnaud Boetsch and Henri Leconte in 1993, Wayne Ferreira in 1994, and Goran Ivanišević in 1995 when India defeated Croatia, beating Jan Siemerink in 1995 to defeat Netherlands, and Jiří Novák in 1997. He teamed up with Bhupathi to beat Hirszon/Ivanisevic of Croatia in 1995, Damm/Korda of the Czech Republic in 1997, Massú/Ríos of Chile in 1997, Broad/Henman in 1998, and Aspelin/Björkman of Sweden in 2005. In 2007, Leander had three wins (two doubles and one singles) and no losses.

Paes first won titles at the Junior US Open and the Junior Wimbledon and he turned professional in 1991. He rose to number 1 in the world junior rankings. In 1992, he reached the quarter finals of the doubles event in the 1992 Barcelona Olympics with Ramesh Krishnan.

His first successful year in the ATP circuit came in 1993, when he partnered with Sébastien Lareau to reach the US Open doubles semifinal. After a moderate season in 1994, he reached the quarter-finals of the 1995 Australian Open doubles with Kevin Ullyett. From 1996, he partnered with fellow-Indian Mahesh Bhupathi. Their first year was not successful, especially in the Grand Slams, reaching the round of 32 only at Wimbledon. 1997 proved to be a much better year for the team, reaching the US Open semifinals. Paes climbed the doubles ranking from no. 89 at the beginning of the year to no. 14 at year end. That year he made his best singles performance in a Grand Slam, losing in the third round of the 1997 US Open to Cédric Pioline after beating Carlos Costa and Arnaud Boetsch.

In 1993 he beat No. 25 Arnaud Boetsch on clay in straight sets. He also defeated Henri Leconte in the same week and even though Ramesh Krishnan closed the tie out by beating Rodolphe Gilbert in a five-setter, the architect of that victory was Paes.

In 1994 he beat World No. 13 Wayne Ferreira in straight sets.

In 1995 he beat Ivanišević (1992 and 1994 Wimbledon singles finalist) in a five-setter on grass. Jan Siemerink, in 1996, then ranked No. 20, also fell to Paes.

At the 1996 Atlanta Olympics he beat Fernando Meligeni to win the bronze medal, the first Indian to win an individual medal since KD Jadhav won bronze at the 1952 Helsinki Olympics. Paes cited the match as one of his greatest performances, in part because his wrist was severely injured. He was awarded the highest sporting honor by the government of India, the Rajiv Gandhi Khel Ratna in 1996.

Paes/Bhupathi grew stronger in 1998, reaching the semifinals of three Grand Slams, the Australian Open, the French Open and the US Open. Paes had two of his biggest singles results. The first one came by winning his only ATP singles title at Newport, and the second was beating Pete Sampras, 6–3, 6–4 at the New Haven ATP tournament at their only meeting. In 1999, the duo reached the finals of all four Grand Slams, winning Wimbledon and the French, thus becoming the first Indians to win a doubles event at a Grand Slam. Paes teamed up with Lisa Raymond to win the mixed doubles event at Wimbledon. The year marked his ascent to the no. 1 doubles ranking. The following year, Paes partnered with Sébastien Lareau for the Australian and Jan Siemerink for the French, losing in the first round on both occasions. Paes again teamed with Bhupathi for the US Open, but lost in the first round again.

In spite of winning the French in 2001, Bhupathi/Paes had first-round exits in the other three Grand Slams. Paes was awarded the Padmashri by the Government of India in 2001. The duo of Paes and Bhupathi won the gold medal at the 2002 Asian Games in Busan. In 2002, Leander paired up with Michael Hill with moderate success.

Paes played at the year-end championships with Bhupathi each year from 1997 to 2000, as well as in 2002 and 2011, reaching three finals. In 1997 they lost the final to Rick Leach and Jonathan Stark. They lost the 1999 final to Sébastien Lareau and Alex O’Brien. In 2000, they lost the final to Donald Johnson and Pieter Norval.

After 2003 Paes increasingly focused on doubles. He won the mixed doubles events at the Australian and Wimbledon with Martina Navratilova, both in 2003. Weeks later, Paes was admitted to the MD Anderson Cancer Center for a suspected brain tumour that was later found to be neurocysticercosis, a parasitic brain infection. He had to miss the US Open, but recovered by the end of that year.

In the 2004 Athens Olympic Games, he paired up with Bhupathi, failing again at the semifinals stage. His next Grand Slam success was in the US Open doubles event in 2006 with Martin Damm. Paes led the Indian tennis team at the Doha Asian Games in 2006 and won two golds in the men’s doubles (with Bhupathi) and mixed doubles (with Sania Mirza). Paes maintained his doubles ranking in the top 20 in the world between 2005 and 2007. With wins in the Rotterdam and Indian Wells, Paes took his doubles tally to 38.

The duo of Leander Paes and Mahesh Bhupathi was nicknamed the ″Indian Express″. Paes’ off-and-on partnership with Bhupathi drew constant media attention in their home country. In the 2006 Asian Games, a loss to the Chinese Taipei team in the team event led Leander to question Bhupathi’s commitment to Team India. He once stated in an interview that although he and Bhupathi are friends, he did not consider pairing with his former teammate. However, for the 2008 Beijing Olympics, they reunited for their country, losing in the quarterfinals to eventual champions Federer/Wawrinka.

In 2009, he won the French Open and US Open Men’s doubles titles with Lukáš Dlouhý and was the runner-up in mixed at the US Open.

In 2010, he joined the Board of Directors of Olympic Gold Quest, a foundation co-founded by Geet Sethi and Prakash Padukone to support talented Indian athletes.

In 2011, the pair won doubles at the Chennai Open. They reunited to play in a Grand Slam Tournament after nine years and claimed runners-up in the 2011 Australian Open and reached the semifinals in the year-end championships.

In the 2012 Summer Olympics, the Indian pair (Vishnu Vardhan) lost to French team Michaël Llodra and Jo-Wilfried Tsonga, 6–7, 6–4, 3–6.

Paes/Štěpánek won the 2013 US Open, defeating Alexander Peya and Bruno Soares 6–1, 6–3. This was Paes’ 3rd US Open men’s doubles title and 14th Grand Slam title. In January 2014, Government of India announced its 3rd Highest Civilian Award Padma Bhushan for Paes.

At the 2015 French Open, Paes started a new partnership with Daniel Nestor. The pair crashed out in the third round; however Paes became just the seventh male player in Open Era to complete 700 doubles wins.

At Wimbledon 2015, Paes teamed up with Martina Hingis to win the mixed doubles championship. The final with a 6–1, 6–1 score against fifth seeds Alexander Peya and Tímea Babos lasted only 41 minutes. Paes/Nestor reached the third round. By winning his 4th Wimbledon mixed doubles title, Paes shared the record for men’s titles in the open era with Owen Davidson.

On 12 September 2015, Paes won the mixed doubles at the 2015 US Open with Hingis, defeating Sam Querrey and Bethanie Mattek-Sands in three sets.

On 3 June 2016, Paes completed his Career Grand Slam in mixed by winning the 2016 French Open with Hingis, thus joining an elite league of players. He broke Davidson’s record for most men’s titles. Paes qualified for the 2016 Summer Olympics in Men’s Doubles, and partnered with Rohan Bopanna. They lost in the first round to the Polish pair of Marcin Matkowski and Łukasz Kubot. He later paired up with Andre Begemann, where they reached the final in the Winston-Salem Open. This pair lost in the first round of the 2016 US Open. He turned up for the Davis cup against Spain with Saketh Myneni, losing to Rafael Nadal and Marc López in 4 sets.

Paes played in the 2017 season with his 111th partner, Andre Sa. The duo lost to the Indian pair of Purav Raja and Divij Sharan in the first round of Aircel Chennai Open in straight sets. With this loss, Paes moved down to 64th in doubles ranks. Though India won their Davis Cup tie against New Zealand, Paes and his last minute partner, Vishnu Vardhan, lost to the New Zealanders Artem Sitak/Michael Venus. Paes and Rohan Bopanna were kept as reserves by new, non-playing captain Mahesh Bhupathi for the tie against Uzbekistan. Eventually, Paes was dropped from final four, which created controversy. Paes reached the semis of the Dubai Open and at Delray Beach. Paes, with Adil Shamasdin, won the Leon Challenger in Mexico. With this victory, he moved to 53rd in the doubles rankings. He then paired with Scott Lipsky and won the Tallahassee Challenger title to move to 49th. Paes and Shamasdin won the Aegon Ilkley Challenger, and Paes moved to 62nd in the rankings. Paes and Purav Raja won the 2017 Knoxville Challenger. With this victory Paes moved to 67th in the rankings. Paes and Purav Raja won the 2017 JSM Challenger of Champaign. With this victory Paes moved to 63rd in the rankings and finished off his 2017 season. It was first time since 1996 that Paes failed to win a title or reach the final at an ATP tour event in a season.

Paes continued his partnership with Raja, losing the Maharashtra Open in the first round to defending champions Bopanna/Jeevan Nedunchezhiyan. In the Australian Open, Paes/Raja lost in the round of 16. Along with James Cerretani, Paes won the Newport Beach Challenger. Paes along with James Cerretani finished as runner up in the Dubai Open. Paes was recalled to India’s Davis Cup squad to play against China. On April 7, 2018, Paes became the most successful player in Davis Cup history with his 43rd doubles victory. After going 0-2 down, Paes/Bopanna scripted India’s comeback and in the end India won the tie 3–2. After this, Paes skipped clay and grass court seasons. Paes was selected for the 2018 Asian Games, but the day before the Games started, he opted out citing the lack of a doubles specialist to accompany him. Paes/Cerretani finished as runner-ups at the Winston-Salem Open. The same pair lost in the first round of the US Open. Paes along with Miguel Ángel Reyes-Varela finished as runner-ups at the Chicago Challenger and Monterrey challenger. Paes along with Miguel Ángel Reyes-Varela won the Santo Domingo Challenger and finished as runner up in Brest Challenger.

Paes and Miguel Ángel Reyes-Varela started the 2019 season at the Maharashtra Open. The duo lost a very close quarter-final to the eventual champions, Bopanna/Divij Sharan, 17–15 in a match tie-break. Paes/Reyes-Varela then finished as runners-up in the Da Nang Challenger before losing in the first round of the Australian Open. Paes reached the semi finals of the Hall Of Fame Championship in July 2019.