Late goal denies Black Cats.
Sunderland were denied three points by a late goal at West Ham but remain unbeaten this season.
The Black Cats looked on course for victory against a combative Hammers side when arch goalscorer Steven Fletcher netted again after just nine minutes.
West Ham had the greater share of the possession for much of the remainder of the match, with Simon Mignolet making a world-class save to deny Kevin Nolan.
But Sunderland defended well and created opportunities of their own on the break without being able to breach Jussi Jaaskelainen's goal a second time.
However, Nolan persisted and eventually netted an equaliser deep into injury time when he scythed a loose ball home from close range.
The late goal will have been a bitter pill to swallow for Martin O'Neill but he can at least take solace in the fact that his side are yet to be beaten with three away trips already undertaken.
Meanwhile the Black Cats ended West Ham's 100% record at home this season.
Sunderland have certainly made the most of scoring opportunities this season and the pattern continued as their talisman continued his goal-filled start to the campaign.
Fletcher has been nothing short of deadly since his move from Wolves, and the hitman took just nine minutes to score for the third game in a row.
A loose ball out of defence was picked off by Seb Larsson, whose clipped cross found Fletcher lurking dangerously in space behind the covering James Collins.
The striker wasn't about to pass up the opportunity, controlling brilliantly before crashing a low shot beyond Jaaskelainen, who got a touch to the ball but couldn't keep it out.
The early goal – Fletcher's fourth in three league outings - was the first conceded by the Hammers at home this season.
Ricardo Vaz Te could have equalised 23 minutes in, but his downward header from Matt Taylor's cross bounced wide.
Having pressed home the advantage early, Sunderland remained lively on the break and threatened when Fletcher's cutting through ball found James McClean, who hurried his shot and fired well wide.
But, urged on by the bruising Mohammed Diame in midfield, the hosts pushed on and generated a trio of serviceable chances just after the half-hour.
Captain Nolan turned a loose ball wide from a tight angle in a packed box before Carlton Cole nodded a Diame cross just over.
Then Nolan, causing problems with his runs from deep, met a punted free-kick with an acrobatic overhead effort only to see the effort flash narrowly wide.
If Fletcher's goal was the most impressive contribution of the half, Mignolet surely ran him close with a world-class stop to deny the busy Nolan just before the break.
Vaz Te beat Danny Rose down the right to hang a cross up for the midfielder, whose flying volley was screaming inside the post before Mignolet sprang left to turn the ball away one-handed.
It was a magnificent intervention from the Belgian, who had little time to react such was the cleanliness of Nolan's strike.
Predictably, West Ham made a strong start to the second half as they chased the game, with Mignolet well placed to gather after Cole flicked on a dangerous ball into the box.
Sunderland's ripostes were mostly limited to counter-attacks as the Hammers pushed forward, although McClean did wriggle free to meet Craig Gardner's cross but couldn't get the desired contact to force the ball goalwards.
Neither did sub David Vaughan, who steamed into the box to meet McClean's 76th-minute cross only to see the ball bounce over him as he dived in with Jaaskelainen drawn to his near post.
Then Fletcher, sniffing a second goal, rifled just over after being teed up on the break.
The visiting defence came under increasing pressure as the minutes ticked by and the Hammers struck just when it looked as if Sunderland's brave resistance might pay off.
With injury time running down, a dangerous ball bobbled around the penalty area and was hooked towards goal by Nolan, who managed to squeeze his shot in between Mignolet and the near post to snatch a point.
- Yellow Jääskeläinen
- Yellow Reid
- Taylor (Jarvis)
- Cole (Maiga)
- Vaz Te (Benayoun)
- Gardner Yellow
- Sessegnon (Campbell)
- Larsson (Vaughan)
- Campbell (Meyler)