The Magpies had looked to have won the game when Harvey Barnes scored in the 86th minute but Yamal equalised from the penalty spot, awarded after Malick Thiaw brought down Dani Olmo.
It means the tie is level heading into next week’s second leg at the Camp Nou.
Anthony Gordon was only fit enough to make the bench due to illness as Eddie Howe made three changes from Saturday’s FA Cup fifth round defeat to Manchester City.
Dan Burn, Joelinton and Jacob Ramsey returned in place of Sven Botman, Joe Willock and Nick Woltemade, with Will Osula preferred to the German and Yoane Wissa up top.
Newcastle made a fast and furious start to the game but couldn’t find the breakthrough in the first half.
The Magpies’ energy continued into the second-half and they deservedly got the opener in the 86th minute when Barnes got on the end of Jacob Murphy’s cross.
The clock had just ticked past the four minutes of stoppage time added when Barcelona were awarded a penalty after Thiaw clipped Olmo. Yamal then stepped up to send Aaron Ramsdale the wrong way.
Here are our Newcastle United player:
Had little to do before facing Lamine Yamal’s late penalty. Would have expected to be busier.
1. Aaron Ramsdale - 7
Had little to do before facing Lamine Yamal’s late penalty. Would have expected to be busier. | Getty Images
Ran himself in the ground before being brought off in the 67th minute. Nullified Raphinha. Experience personified.
2. Kieran Trippier - 8
Ran himself in the ground before being brought off in the 67th minute. Nullified Raphinha. Experience personified. | AFP via Getty Images
Defended extremely well right up until the final second when he brought down Dani Olmo for a Barca penalty.
3. Malick Thiaw - 6
Defended extremely well right up until the final second when he brought down Dani Olmo for a Barca penalty. | Getty Images
In all the right positions defensively. So unlucky not to come away with a clean sheet.
4. Dan Burn - 8
In all the right positions defensively. So unlucky not to come away with a clean sheet. | Getty Images