Thompson had been out indefinitely due to a concussion suffered in Game 5 of the Western Conference finals May 27 against the Houston Rockets.
Thompson returned to practice Monday, after which he said he needed a "couple more days to get completely right, and I expect to be fully healthy and compete on Thursday." After practice Tuesday, Thompson said he was "99.9 percent sure" he would be cleared for the opener against the Cleveland Cavaliers on Thursday night.
The Warriors announced that he had cleared the NBA protocol later Tuesday.
"I feel great honestly," Thompson said. "These last few days I feel like I've gotten my wind back, and tomorrow's the final tuneup. Just trying to stop the nerves and anxiousness."
When asked about the team doctors in charge of clearing him, Thompson said, "I'm just trying to do everything to get prepared. They do have my best interests, so that's how I look at it."
Warriors coach Steve Kerr assessed Thompson's progress, saying, "He's done everything. He looks fine."
When asked if the concussion protocol needs to be re-examined, Kerr said, "It's not my department. I coach basketball. I'm all for safety."
Warriors forward Marreese Speights, who missed the last eight playoff games with a calf injury, also will be available for Game 1, Kerr said.