The north London side saw three goals chalked off by officials during Thursday evening's 0-0 Europa League draw with Serie A outfit Lazio at White Hart Lane
The 29-year-old American, who was making his full debut for the club following his move from Fulham, believes his goal should have stood after he headed one into Lazio's net off a pass from Gareth Bale in the 22nd minute. It was the American midfielder's first home game with the club.
“I thought I was level with the line, it was a good ball from (Gareth) Bale, I got on the end of it and thought I opened my account but it was offside," Dempsey told ITV.
“That's the way it goes sometimes but they defended well, set up to counterattack and were tough to break down but we had some chances and were unlucky to get the goal tonight."
Dempsey was starting for the first time in two games since joining Spurs from Fulham at the transfer deadline.
“It's good to get games and get more minutes," he said. "I'm trying to create chances, get on the end of things, I can play other positions but they were tough and sat back and played on the counter. But we did have some chances and were unlucky not to get a goal.”
The north London side also had strikes from Jermain Defoe and Steven Caulker ruled out by officials at White Hart Lane, as it kicked off its Group J campaign with a stalemate.