The Baggies had looked set to take the bragging rights when Shane Long struck twice inside 11 minutes with a couple of outstanding finishes.
Stephane Sessegnon then wasted two gilt-edged chances to kill the game before a triple substitution by Paul Lambert turned it on its head.
The Villans suddenly had the impetus and pulled one back when Karim El Ahmadi hooked in a clever finish after a flick-on left him in acres of space on the right side of the area.
And they secured a share of the spoils 14 minutes from time when Westwood seized upon a loose ball and sizzled a stunning drive into the corner to mark his first goal for the club in style.
No Premier League team has recovered more points from losing positions than Villa this season. (via Opta Joe)
West Brom are unbeaten in their last six Premier League games against Aston Villa. Shane Long's second was the 300th goal scored in the Premier League this season.
That was the first time Shane Long has scored twice in one Premier League match (via Infostrada)
Aston Villa's last six Premier League goals have come after half-time. (via Opta Joe)
PRE-MATCH - One change for WBA, Benteke starts for unchanged Villans. Goran Popov comes in for his first Premier League start of the season in place of Liam Ridgewell for the Baggies while Benteke shakes off a knee injury sustained on international duty to ensure Villa are unchanged from the win over Cardiff.
3' GOAL! WBA 1-0 VILLA - Chris Brunt's sensational diagonal ball over the top is plucked out of the air by the deftest of touches by Long who then cuts inside and flashes a low shot into the corner. Great start for the hosts.
6' CLOSE! - Tonev cuts in from the left and arrows in a shot that deflects off Gareth McAuley and is brilliantly beaten away by Boaz Myhill at his near post.
11' GOAL! WBA 2-0 VILLA - A slack pass by Leandro Bacuna is seized upon by Long who jinks beyond Nathan Baker before clipping a delightful finish over the advancing Guzan.
18' WHAT A MISS! It should be 3-0. Morgan Amalfitano catches Villa napping down the right and whips in a sublime cross for Stephane Sessegnon who somehow contrives to steer his free header wide at the back post.
24' CLOSE! Villa finally put together an attack and Libor Kozak sees a rasping half volley from 25 yards clip the top of the bar following a clever flick on by Beneteke.
57' TRIPLE SUB FOR VILLA - Fabian Delph on for Sylla, Gabriel Agbonlahor on for Kozak and Andreas Weimann on for Tonev as Paul Lambert gambles to get back in this.
59' CLOSE! Villa's triple sub almost pays off straight away as Weimann's low shot takes a wicked deflection and just about bobbles wide via the feet of Myhill.
64' IT SHOULD BE THREE! Amalfitano exchanges a one-two with Sessegnon and powers to the byline where he cuts it back for the Benin international, who again wastes a glorious chance by blazing over from six yards out.
67' GOAL! WBA 2-1 VILLA! The visitors are back in it. A ball is headed on in the WBA area, allowing Karim El Ahmadi to hook a shot over the keeper. Game on!
76' GOAL! WBA 2-2 VILLA! It's all square! A wonderful first touch allows Ashley Westwood to pick up the ball 25 yards out and lash an unstoppable drive into the corner. What a comeback! TALKING POINT
Match-saving management: Another West Midlands derby ends all-square for a fourth straight time and it's all down to the triple substitution by Paul Lambert. With his side all-but down and out, the Scot threw on Gabriel Agbonlahor, Fabian Delph and Andreas Weimann. It gave the visitors the impetus to have a right go at WBA and in the end they got a hard-fought point.
MAN OF THE MATCH
Shane Long (West Brom) - A constant thorn in Villa's side during the first half. Took both of his goals brilliantly, showing magnificent control and technique in the lead up to each strikes. Deserved to be on a winning side.
WBA: Myhill 6, Reid 6, McAuley 6, Olsson 6, Popov 6, Mulumbu 6, Yacob 7, Amalfitano 7, Sessegnon 5, Brunt 7, Long 8. Subs: Morrison 6, Anichebe 6.
ASTON VILLA: Guzan 6, Bacuna 5, Vlaar 7, Clark 5, Baker 5, El Ahmadi 7, Westwood 7, Sylla 6, Tonev 6, Benteke 6, Kozak 6. Subs: Weimann 7, Delph 6, Agbonlahor 7.
THE MATCH IN A TWEET