| Doubles | |
|---|---|
| 2003 U.S. Men's Clay Court Championships | |
| Champions |  Mark Knowles  Daniel Nestor |
| Runners-up |  Jan-Michael Gambill Graydon Oliver |
| Final score | 6–4, 6–3 |
Mardy Fish and Andy Roddick were the defending champions but lost in the semifinals to Mark Knowles and Daniel Nestor.
Knowles and Nestor won in the final 6–4, 6–3 against Jan-Michael Gambill and Graydon Oliver.
Champion seeds are indicated in bold text while text in italics indicates the round in which those seeds were eliminated.
Mark Knowles / Daniel Nestor (champions) Jan-Michael Gambill / Graydon Oliver (final)
Sebastián Prieto / 
André Sá (first round) Devin Bowen / 
Ashley Fisher (semifinals)| First round | Quarterfinals | Semifinals | Final | ||||||||||||||||||||||||
| 1 | M Knowles D Nestor | 3 | 6 | 71 | |||||||||||||||||||||||
| WC | P Goldstein R Kendrick | 6 | 1 | 61 | 1 | M Knowles D Nestor | 6 | 6 | |||||||||||||||||||
| M Merklein J Morrison | 6 | 6 | M Merklein J Morrison | 3 | 1 | ||||||||||||||||||||||
| WC | J Blake T Blake | 4 | 4 | 1 | M Knowles D Nestor | 3 | 6 | 6 | |||||||||||||||||||
| 3 | S Prieto A Sá | 1 | 2 | M Fish A Roddick | 6 | 3 | 2 | ||||||||||||||||||||
| M Fish A Roddick | 6 | 6 | M Fish A Roddick | 7 | 6 | ||||||||||||||||||||||
| J Thomas B Vahaly | 6 | 6 | J Thomas B Vahaly | 5 | 3 | ||||||||||||||||||||||
| T Dent C Mamiit | 4 | 2 | 1 | M Knowles D Nestor | 6 | 6 | |||||||||||||||||||||
| B MacPhie T Martin | 5 | 4 | 2 | J-M Gambill G Oliver | 4 | 3 | |||||||||||||||||||||
 S Aspelin  N Kiefer | 7 | 6 | S Aspelin N Kiefer | ||||||||||||||||||||||||
 T Shimada  M Wakefield | 4 | 5 | 4 | D Bowen A Fisher | w/o | ||||||||||||||||||||||
| 4 | D Bowen A Fisher | 6 | 7 | 4 | D Bowen A Fisher | 66 | 5 | ||||||||||||||||||||
| J Gimelstob S Humphries | 3 | 6 | 6 | 2 | J-M Gambill G Oliver | 78 | 7 | ||||||||||||||||||||
 K Carlsen  J Melzer | 6 | 3 | 3 | J Gimelstob S Humphries | 5 | 6 | 66 | ||||||||||||||||||||
 L Horna S Roitman | 4 | 0r | 2 | J-M Gambill G Oliver | 7 | 4 | 78 | ||||||||||||||||||||
| 2 | J-M Gambill G Oliver | 6 | 1 | ||||||||||||||||||||||||
The 2002 Canada Masters doubles was the men's doubles event of the one hundred and thirteenth edition of the Canada Masters; a WTA Tier I tournament and the most prestigious men's tennis tournament held in Canada. Jiří Novák and David Rikl were the defending champions but they competed with different partners that year, Novák with Radek Štěpánek and Rikl with David Prinosil. Novak and Štěpánek lost in the second round to Mark Knowles and Daniel Nestor. Prinosil and Rikl lost in the semifinals to Bob Bryan and Mike Bryan. The Bryans won in the final 4–6, 7–6(7–1), 6–3 against Knowles and Nestor.
The 2001 Canada Masters doubles was the men's doubles event of the one hundred and twelfth edition of the Canada Masters; a WTA Tier I tournament and the most prestigious men's tennis tournament held in Canada. Sébastien Lareau and Daniel Nestor were the defending champions but they competed with different partners that year, Lareau with Justin Gimelstob and Nestor with Sandon Stolle. Gimelstob and Lareau lost in the first round to Mark Knowles and Brian MacPhie, as did Nestor and Stolle to Jan-Michael Gambill and Simon Larose. Jiří Novák and David Rikl won in the final 6–4, 3–6, 6–3 against Donald Johnson and Jared Palmer.
Mark Knowles and Daniel Nestor were the defending champions, but lost in the final to Michaël Llodra and Fabrice Santoro.
Jan-Michael Gambill and Scott Humphries were the defending champions but they competed with different partners that year, Gambill with Jonathan Stark and Humphries with Justin Gimelstob.
Mahesh Bhupathi and Leander Paes were the defending champions but only Paes competed that year with John-Laffnie de Jager.
Jonas Björkman and Todd Woodbridge were the defending champions but lost in the final 6–2, 6–4 against Mahesh Bhupathi and Jan-Michael Gambill.
Karsten Braasch and André Sá were the defending champions but did not compete that year.
Rick Leach and David Macpherson were the defending champions but lost in the semifinals to Jan-Michael Gambill and Graydon Oliver.
Mark Knowles and Daniel Nestor won in the final 6–3, 7–5, 6–0 against Mahesh Bhupathi and Max Mirnyi.
Jonas Björkman and Todd Woodbridge were the defending champions but did not compete that year.
Wayne Black and Kevin Ullyett were the defending champions but only Black competed that year with Mark Philippoussis.
Martin Damm and Cyril Suk were the defending champions but lost in the semifinals to Michaël Llodra and Fabrice Santoro.
The 2003 Hamburg Masters doubles was a German tennis event.
Nicolas Escudé and Fabrice Santoro were the defending champions but only Santoro competed that year with Michaël Llodra.
Mark Knowles and Daniel Nestor were the defending champions but lost in the semifinals to James Blake and Mardy Fish.
Jared Palmer and Richey Reneberg were the defending champions but only Reneberg competed that year with Jim Grabb.
Wayne Ferreira and Yevgeny Kafelnikov were the defending champions but lost in the first round to David Rikl and Daniel Vacek.
Yevgeny Kafelnikov and Andrei Olhovskiy were the defending champions but only Olhovskiy competed that year with Ken Flach.
Grant Connell and Patrick Galbraith were the defending champions but they competed with different partners that year, Connell with Byron Black and Galbraith with Jonathan Stark.
Trevor Kronemann and David Macpherson were the defending champions but lost in the semifinals to Mark Knowles and Daniel Nestor.