Thus far he has won 88 men’s doubles titles (with 10 different partners), including a Gold medal at the 2000 Summer Olympics, four ATP World Tour Finals, and eight Grand Slam men’s doubles titles attained with three different partners. In addition, Nestor has won 4 Grand Slam mixed doubles titles: 2007 Australian Open with Elena Likhovtseva, the 2011 Australian Open with Katarina Srebotnik, and the 2013 Wimbledon and 2014 Australian Open with Kristina Mladenovic. His 88 men’s doubles titles make him the third most decorated champion among doubles players. He was the first player in doubles tennis history to win every Grand Slam and Masters Series event, the Year End Championships and Olympic gold medal at least once in his career. He was named ATP Doubles Team of the Year in 2002 and 2004 (with Mark Knowles) and 2008 (with Nenad Zimonjic). He became the World No. 1 ranked doubles player in the world in August 2002. Nestor’s career-high singles ranking is World No. 58, which he reached in August 1999.

Nestor won three Grand Slam doubles titles together with longtime partner Mark Knowles of the Bahamas. The tandem won the 2002 Australian Open, the 2004 US Open and the 2007 French Open. He and Knowles also reached the final of the 1995 Australian Open, the 1998 French Open and US Open, the 2002 French Open and Wimbledon and the 2003 Australian Open. Nestor won three Grand Slam titles with Nenad Zimonjic (2008 Wimbledon, 2009 Wimbledon and 2010 French Open) and two with Max Mirnyi (2011 French Open and 2012 French Open). He also reached two more finals with Zimonjic, the 2008 French Open and 2010 Australian Open.

In mixed doubles, he reached his first final at the 2003 US Open with Lina Krasnoroutskaya. He made it to the 2006 Australian Open and 2006 French Open finals, as well as winning the mixed doubles event at the 2007 Australian Open with partner Elena Likhovtseva. He won his second mixed doubles title at the 2011 Australian Open with Katarina Srebotnik. Nestor won the 2013 Wimbledon mixed doubles title with Kristina Mladenovic (they also reached the 2013 French Open and 2015 Australian Open mixed doubles finals together). In 2014, Nestor won his third Australian Open title, and his second Grand Slam title with Mladenovic, and this partnership has yielded his best stretch of mixed doubles results, with one semi-final appearance, one runner-up finish and two Grand Slam titles in the past four Grand Slam events.

At the 2000 Summer Olympics in Sydney, Australia, Nestor and partner Sébastien Lareau won a gold medal, the first and only medal so far in tennis for Canada. The duo won four more titles together during their career, which was highlighted by an ATP Masters 1000 win in Canada. After the Olympics, Nestor won one title with Kevin Ullyett in November 2000 and two with Sandon Stolle in 2001.

He has been a member of the Canadian Davis Cup team since 1992. He first came to prominence in the public eye that year by defeating then world number one Stefan Edberg in a hard-fought singles match in Vancouver. He was part of the squad who made history for Canada in 2013 as they were the first Canadian team in the Open Era to reach the World Group semifinals.

Nestor won his first doubles title in Bogotá, Colombia with Mark Knowles in 1994. They defeated French Open champions Luke and Murphy Jensen in the final.

On July 5, 2006, he participated in the second-longest match in Wimbledon history, lasting 6 hours and 9 minutes.

2007 was a year of change for Nestor. He and long-time doubles partner Knowles announced that they were parting ways after the 2007 US Open (the two won 40 titles together, including 3 Grand Slams, 1 ATP year-end finals, and 15 ATP Masters 1000 titles), as Nestor began a new partnership with Nenad Zimonjic. Nestor and Zimonjic had actually won an ATP World Tour 250 Series event together back in 2001. They won the first title of their official partnership at the 2007 St. Petersburg Open, then advanced to the 2007 Paris Masters final as the second seeds. Nestor and Knowles partnered once more at the 2007 Tennis Masters Cup after having qualified for the year-end event as the top seed. Their finals win over Simon Aspelin and Julian Knowle earned them their first Tennis Masters Cup title at the year-end doubles tournament, and was a fitting end for one of the most successful doubles teams to ever play the game.

In 2008 (their first full season), Nestor and Zimonjic won the first major title of their partnership at the Hamburg Masters. They reached the final of the French Open a week later. Nestor and Zimonjic then captured the 2008 Wimbledon title, winning over Jonas Björkman and Kevin Ullyett. This was Nestor’s first Wimbledon title, and in doing so, he completed a Career Grand/Golden Slam. The pair also captured the 2008 Tennis Masters Cup that year.

In 2009, the pair won Wimbledon again and eight additional titles, five of which were Masters 1000 events – personal bests for both in terms of numbers of Masters 1000 and overall titles won in a single year. In 2010, Nestor and Zimonjic won the French Open and were runners-up at the Australian Open. They finished their partnership on a high note by winning the ATP World Tour Finals in London. Between 2008 and 2010, the duo won 21 ATP titles and reached 9 more finals. The pair have currently won 27 titles together, which includes 3 Grand Slams, 2 ATP year-end finals, and 10 ATP Masters 1000 titles.

Nestor paired up with Max Mirnyi from 2011-2012. In his first tournament with Max Mirnyi in Brisbane, he won his 783rd career doubles match, overtaking Todd Woodbridge for the all-time match wins record. Nestor and Mirnyi won the 2011 French Open and the 2011 ATP World Tour Finals in London. In the final of the ATP World Tour Finals, he played his 1,148th match, an all-time record. Nestor won one more Grand Slam title with Mirnyi when they captured their second straight French Open in 2012. Nestor won a total of eight titles during his partnership with Mirnyi, which includes the 2 Grand Slams, 1 ATP year-end finals, and 1 ATP Masters 1000 title in Shanghai.

Starting in January 2013, Nestor partnered with Mahesh Bhupathi, and played with Robert Lindstedt later that year. Nestor won his 81st doubles title, the Winston-Salem Open, in August with new partner Leander Paes. He also became the first player in ATP history to score 900 career doubles wins.

At the first tournament of his season, the 2014 Brisbane International, Nestor partnered with Mariusz Fyrstenberg and won his 82nd doubles title. Frysenberg was the 8th partner of Nestor’s career with which he won a doubles title. At the end of 2013, he teamed up with former partner Nenad Zimonjic for the 2014 season, and at the 2014 Apia International Sydney, Zimonjic and Nestor captured his second doubles title. He won his third doubles title of the season and 84th of his career at the 2014 Mutua Madrid Open, surpassing Todd Woodbridge for 3rd overall in ATP history. Nestor and Zimonjic won their second consecutive Masters 1000 title at the 2014 Internazionali BNL d’Italia. By year end Nestor rose to number 3 overall and he and Zimonjic clinched a spot in the ATP Tour finals.

In January 2015 at the Apia International Sydney, Nestor won his 86th doubles title, giving him at least one men’s doubles title per year for 22 straight years and putting him in sole position of 10th overall for ATP titles in the Open era. This was Nestor’s first title with new partner Rohan Bopanna, his 9th different partner. He won his second doubles title of the season at the Dubai Tennis Championships in February. In August at the Cincinnati Masters, Nestor won his third title of the season and his first with new partner Édouard Roger-Vasselin.