Greg Rusedski was the defending champion of the singles event of the Heineken Open tennis tournament, held in Auckland, New Zealand, but did not compete that year.
|2003 Heineken Open|
|Draw||32 (4 Q / 3 WC )|
Fourth-seeded Gustavo Kuerten won in the final 6–3, 7–5 against unseeded Dominik Hrbatý.
A champion seed is indicated in bold text while text in italics indicates the round in which that seed was eliminated.
- Jiří Novák (quarterfinals)
- David Nalbandian (first round)
- Fernando González (second round)
- Gustavo Kuerten (champion)
- José Acasuso (first round)
- Jan-Michael Gambill (second round)
- Guillermo Coria (quarterfinals)
- Davide Sanguinetti (first round)
- Q = Qualifier
- WC = Wild card
- LL = Lucky loser
- Alt = Alternate
- SE = Special exempt
- PR = Protected ranking
- ITF = ITF entry
- JE = Junior exempt
- w/o = Walkover
- r = Retired
- d = Defaulted
- SR = Special ranking
- ^ "2003 Auckland – Singles draw". Association of Tennis Professionals (ATP).