The 2005 Portland Grand Prix was the sixth race for the 2005 American Le Mans Series season held at Portland International Raceway. It took place on July 30, 2005.
Class winners in bold. Cars failing to complete 70% of winner's distance marked as Not Classified (NC).
| Pos | Class | No | Team | Drivers | Chassis | Tyre | Laps | |
|---|---|---|---|---|---|---|---|---|
| Engine | ||||||||
| 1 | LMP1 | 2 |  ADT Champion Racing |  Frank Biela Emanuele Pirro | Audi R8 | 137 | ||
| Audi 3.6L Turbo V8 | ||||||||
| 2 | LMP1 | 20 | Dyson Racing | Chris Dyson Andy Wallace | MG-Lola EX257 | 137 | ||
| MG (AER) XP20 2.0L Turbo I4 | ||||||||
| 3 | LMP1 | 16 | Dyson Racing | Butch Leitzinger James Weaver | MG-Lola EX257 | 136 | ||
| MG (AER) XP20 2.0L Turbo I4 | ||||||||
| 4 | LMP2 | 37 | Intersport Racing | Clint Field Gregor Fisken | Lola B05/40 | 132 | ||
| AER P07 2.0L Turbo I4 | ||||||||
| 5 | GT1 | 4 | Corvette Racing | Oliver Gavin Olivier Beretta | Chevrolet Corvette C6.R | 131 | ||
| Chevrolet 7.0L V8 | ||||||||
| 6 | GT1 | 3 | Corvette Racing |  Ron Fellows Johnny O'Connell | Chevrolet Corvette C6.R | 131 | ||
| Chevrolet 7.0L V8 | ||||||||
| 7 | LMP1 | 12 | Autocon Motorsports | Bryan Willman Michael Lewis | Riley & Scott Mk III C | 130 | ||
| Elan 6L8 6.0L V8 | ||||||||
| 8 | GT1 | 5 | Pacific Coast Motorsports | Alex Figge Ryan Dalziel | Chevrolet Corvette C5-R | 130 | ||
| Chevrolet 7.0L V8 | ||||||||
| 9 | GT1 | 35 | Maserati Corse Risi Competizione | Fabrizio de Simone Mika Salo | Maserati MC12 | 129 | ||
| Maserati 6.0L V12 | ||||||||
| 10 | GT2 | 23 | Alex Job Racing | Timo Bernhard Romain Dumas | Porsche 911 GT3-RSR | 125 | ||
| Porsche 3.6L Flat-6 | ||||||||
| 11 | GT2 | 43 | BAM |  Martin Jensen Wolf Henzler | Porsche 911 GT3-RSR | 124 | ||
| Porsche 3.6L Flat-6 | ||||||||
| 12 | GT2 | 45 | Flying Lizard Motorsports | Johannes van Overbeek Jon Fogarty | Porsche 911 GT3-RSR | 124 | ||
| Porsche 3.6L Flat-6 | ||||||||
| 13 | GT1 | 71 | Carsport America | Michele Rugolo Tom Weickardt | Dodge Viper GTS-R | 123 | ||
| Dodge 8.0L V10 | ||||||||
| 14 | GT2 | 50 | Panoz Motor Sports | Bryan Sellers Robin Liddell | Panoz Esperante GT-LM | 123 | ||
| Ford (Elan) 5.0L V8 | ||||||||
| 15 | GT2 | 51 | Panoz Motor Sports | Marino Franchitti Christophe Tinseau | Panoz Esperante GT-LM | 122 | ||
| Ford (Elan) 5.0L V8 | ||||||||
| 16 | GT2 | 79 | J3 Racing | Justin Jackson Michael Galati | Porsche 911 GT3-RSR | 120 | ||
| Porsche 3.6L Flat-6 | ||||||||
| 17 | GT2 | 44 | Flying Lizard Motorsports | Lonnie Pechnik Seth Neiman | Porsche 911 GT3-RSR | 120 | ||
| Porsche 3.6L Flat-6 | ||||||||
| 18 | LMP2 | 8 | B-K Motorsport | Guy Cosmo Jamie Bach | Courage C65 | 117 | ||
| Mazda R20B 2.0L 3-Rotor | ||||||||
| 19 | GT2 | 31 | Petersen Motorsports White Lightning Racing | Patrick Long Jörg Bergmeister | Porsche 911 GT3-RSR | 113 | ||
| Porsche 3.6L Flat-6 | ||||||||
| 20 DNF | GT2 | 24 | Alex Job Racing | Ian Baas Darren Law | Porsche 911 GT3-RSR | 95 | ||
| Porsche 3.6L Flat-6 | ||||||||
| 21 DNF | LMP2 | 10 | Miracle Motorsports | Jeff Bucknum Chris McMurry | Courage C65 | 86 | ||
| AER P07 2.0L Turbo I4 | ||||||||
| 22 DNF | GT1 | 63 | ACEMCO Motorsports | Terry Borcheller Johnny Mowlem | Saleen S7-R | 48 | ||
| Ford 7.0L V8 | ||||||||
| 23 DNF | LMP1 | 1 | ADT Champion Racing | Marco Werner JJ Lehto | Audi R8 | 48 | ||
| Audi 3.6L Turbo V8 |