Spurs created the better chances in an open and entertaining match but Sporting striker Paulinho broke the deadlock in the 90th minute with a glancing header from a corner.
Tottenham Hotspur suffered their first defeat of the season as Sporting snatched a 2-0 home win over Antonio Conte's side in the UEFA Champions League on Tuesday with goals in added time from substitutes Paulinho and Arthur Gomes.
Spurs created the better chances in an open and entertaining match but Sporting striker Paulinho broke the deadlock in the 90th minute with a glancing header from a corner.
Brazilian forward Gomes, who had only come onto the pitch after the goal, made sure of the victory with a superb strike in the second minute of added time, finishing from close range after a breathtaking run into the box.
The victory means Sporting lead Group D with six points, with Tottenham second on three after two games.
"It feels great. Winning like that at the end, after we put in a hard shift, we couldn’t be happier," said Sporting livewire Marcus Edwards, who started out as a trainee at Spurs. "We deserved it. We showed how we can play."
Spurs coach Antonio Conte was unhappy with the way his side collapsed at the end of a tricky encounter.
"For sure we are frustrated because the game was balanced and we tried to win the game in the second half," he said.
"But in the last 10 minutes we can do much better. They score with a corner, then we conceded the second goal after the 90 minutes. It’s a pity, a difficult game for sure."
Club Brugge pulled off a shock 4-0 win at FC Porto on Tuesday to win a second successive Champions League Group B game and go top of the standings.
An early penalty converted by Ferran Jutgla was followed by two quick goals after halftime from Kamal Sowah and Andreas Skov Olsen before a late effort from teenage substitute Antonio Nusa put the seal on a massive upset.
The Belgian champions were worthy winners as they added an unexpected triumph to last week’s home success over Bayer Leverkusen.
Brugge moved to six points, ahead of Leverkusen and Atletico Madrid who have three each after the German side beat the Spaniards 2-0 also on Tuesday. Porto are bottom with no points.