Fears about Walcott's fitness emerged when he was forced to limp off during last weekend's Premier League game against Chelsea, after appearing to suffer a hamstring strain in the 0-0 draw.
But Wenger revealed the injury is not as severe as first thought, with the winger likely to be available before the end of the domestic season and certainly fit for selection in the England squad for the tournament in Poland & Ukraine.
"It is less serious than we thought. He has a small chance to play in the last game [of the season]," Wenger said. "For the Euros, he is definitely available.
"I think in fact the injury of Walcott is good news for England because he just has a little rest. He had enough competition and now he has a little rest before going there so he should be in a good frame of mind and physically fit."
Walcott has scored 11 goals so far this season, and Wenger believes that is evidence he has had his best season to date at the club - although he does not believe the former Southampton prodigy gets the credit he deserves because of the potential he exhibited from a young age.
"Theo gets criticism because he raises the level of expectation so much that when he has a disappointing game or doesn't make the difference, people straight away go at him because they expect something special," he said.