Substitute Leandro Trossard scored his first goal for Arsenal but the Premier League leaders missed the chance to move eight points clear at the top as Ivan Toney earned resilient Brentford a deserved point.
After a goalless first half in which the Bees hit the woodwork through Toney, the Gunners took the lead when Trossard struck at the back post four minutes after coming off the bench.
But Brentford got the reward their excellent away performance deserved when Toney nodded in Christian Norgaard’s cross from close range.
There was a lengthy check by the video assistant referee for a possible offside in the build-up but the goal was eventually confirmed.
Arsenal raised the tempo in the closing stages – including seven minutes of added time – as they searched for a winner but Brentford completed an excellent all-round defensive display by holding firm for a point.
Arsenal face Manchester City – six points behind before their game against Aston Villa – in a top-of-the table showdown on 15 February.
If Pep Guardiola’s side win on Sunday afternoon, they would reduce the deficit to three by the time the top two meet.
Brentford, meanwhile, are eighth and just five points off fifth.
Arsenal title hopes dented by resilient Brentford
Arsenal have been formidable at home this season, winning eight and drawing one of their nine games at the Emirates before the visit of Brentford.
They are one of two sides, along with Newcastle United, in the top flight who are unbeaten on their own turf – but that record was given a stern test against in-form Brentford, who had won four of their previous five league games.
Mikel Arteta’s side had plenty of possession but found little joy in unlocking a disciplined Bees defence until their patience was rewarded when Trossard struck midway through the second half.
The Belgium forward has looked a fine addition since joining from Brighton & Hove Albion for £27m last month and he was close to adding a second soon after with a shot from distance.
But a one-goal lead rarely looked like it would be enough against a Brentford side who had been sharp in attack, and so it proved when Toney equalised.
The draw for Arsenal follows successive defeats in the league and FA Cup to Everton and Manchester City respectively.
How they respond to this relative stumble – not least in Wednesday’s home game against City – will be key in determining whether they can win a first Premier League title since 2003-04.
In-form Bees eyeing Europe
After finishing a commendable 13th in their first Premier League season last term, Brentford are having another fine campaign and are pushing for a European place.
Thomas Franks’ side had not conceded a goal in their three league games before the trip to Arsenal and it was clear to see why they are such a difficult side to break down.
They kept their shape despite Arsenal enjoying the majority of possession and responded brilliantly to the Gunners taking the lead to became one of only two sides this season to take anything away from the Emirates.
Toney’s goal was his 15th of the season – only Erling Haaland and Harry Kane have scored more – and with the Bees having an excellent defence allied to his threat, there is every chance they can secure European football next season.
