The England U18s international made his senior bow off the bench as Spurs came from two-down to defeat Burnley 4-2 in The FA Cup on Wednesday.
Midfielder Onomah helped his country win the European U17 Championship last summer, and he has progressed this season to make nine appearances for the club’s U21 side before his big moment arrived at White Hart Lane.
"I’ve been waiting for it my whole life and now I’m speechless"
Josh Onomah after his debut
"It feels amazing. I’ve been waiting for it my whole life, and now that it’s come I’m speechless," he told TottenhamHotspur.com after the game.
"It’s such a happy moment, I’m so proud and a bit lost for words really."
It was the third time that the 17-year-old had been named on the bench for the senior team, but having failed to come on previously, he says he was prepared when boss Mauricio Pochettino gave him the nod to go on.
"When he called me I was ready," he said. "Usually I’d be nervous, but I was ready and just buzzing. I was focussed and just trying to get my mind ready for the game.
"It was a good game. We were unfortunate to concede early on, but we got back and I was just happy to get on the pitch – it was a good experience."
The youngster will be hoping that he has done enough to be included in the squad for Saturday’s Premier League clash at home to Sunderland.