The Three Lions face Sweden in Olomouc on Sunday, aiming to put the 1-0 defeat in their opening game behind them.
Sweden v England
UEFA European U21 Championship
The Finals
5pm (BST), Sunday 21 June 2015
Olomouc, Czech Republic
Live on BT Sport
And the Tottenham Hotspur striker is confident England can get back to winning ways and progress with two group qualifiers still to play.
"We’re obviously a bit gutted, you never want to start a tournament with a loss," he said, after the game in Uherske Hradiste.
"It’s disappointing but there’s still a long way to go and we know what we have to do.
"We know we have to stick together and there’s two games left so we know what we have to do and we have to try and look forward to Sunday.
"It’s a game which we can win for sure."
Kane endured a frustrating evening against Portugal, with keeper Jose Sa making a fine first-half save to deny him and a couple of near misses after that.
And whilst the 21-year-old knows that England can perform better, he felt there were plenty of positives to take from the game.
"I didn’t think we did too badly, especially in the first half when we had a few shots on target and their keeper made some good saves," he added.
"Jesse [Lingard] kept cutting in off the left, the midfielders were getting in and having a few shots and myself as well.
"They got a ricocheted goal and on another day, it might have gone our way but that’s what we’ve got to learn from.
"There are a couple of things we can work on but we’ve got to go back, regroup and go again on Sunday - it’s a short time before the next game."
Kane comes into the Euro Finals on the back of a busy campaign, which has seen him play over 50 games for club and country.
But the Walthamstow-born hitman says he feels as fit and strong as ever to lead the England line in Czech Republic.
"I feel fine," he revealed.
"Physically, it’s not a problem. As an athlete, you’re built to do that so that isn’t an excuse.
"We had a great qualifying campaign and it’s a great group of lads, probably the best I’ve been involved since I’ve been coming up the ranks with England.
"We all get on very well, so this won’t affect us and we’ll stick together, we know what we have to do now."