Carroll, out injured since the turn of the year, was sent on as a last throw of the dice by manager David Moyes with West Ham trailing to Peter Crouch's goal.
"I thought all three subs played really well when they came on but I have to say, I didn't think we'd need them because I thought we had played well enough to be in front", Moyes explained.
The former Liverpool striker's first goal since November put relegation-threatened Stoke within touching distance of their first win in 10 games.
Considering Stoke boss Paul Lambert had said pre-match his side needed to win three of their final five games to stay up it was surprising they seemed to show little attacking intent for much of the game and Jack Butland was by far the busier goalkeeper.
BC-SOC-West Ham-Stoke, 1st Ld-Writethru, 408 Carroll equalizes late as West Ham holds Stoke to 1-1 in EPLAP Photo LON606, LON816Eds: Updates with detail, quotes.
Lambert reflected afterwards: 'It is a blow because we were so close to winning. "A win on Sunday would really set the cat among the pigeons".
Things are pretty rosy for West Ham at the moment after their point at Chelsea gave them a bit of breathing space above the bottom three.
Butland made a vital save to keep out West Ham's best chance of the first half as Marko Arnautovic's point-blank volley hit his old team-mate in the face.
Police have warned social media trolls they could be committing a criminal offence by abusing referee Michael Oliver and his wife Lucy.
The Hammers thought they had won the game when Javier Hernandez scored in injury time, but it was disallowed for a Carroll handball in the build-up.
Then a low Edimilson Fernandes drive flew past Butland but Arnautovic, this time clearly offside, was in the keeper's way.