The Baggies looked to be hanging on for only the second win of the season - they beat Wanderers to achieve their first - after Zoltan Gera had fired them into a 13th minute lead.
Wanderers monopolised the play after that, Jay-Jay Okocha hitting the bar while having another shot cleared off the line, but they finally drew level seven minutes from time when El Hadji Diouf fired in from close range.
Kevin Davies was a constant nuisance to the Albion defence in the early stages but Bolton have failed to keep a clean sheet in their last 12 league games and they conceded a goal in the visitors' first serious attack in the 13th minute.
Gera beat Ricardo Gardner on the edge of the area before placing his shot just outside the reach of veteran keeper Kevin Poole and into the corner of the net.
Albion should have doubled their lead a minute later. Radhi Jaidi missed his header but Geoff Horsfield, with only the keeper to beat, pulled his shot wide of the target.
Wanderers stepped up the pace as they tried to get back into the game and the Albion defence was lucky to survive in the 29th minute.
First Davies cut in from the by-line to fire at goal, but Russell Hoult was able to charge the shot down and when the ball broke to Okocha his shot was cleared off the line.
Bolton should have been back in the game in the 52nd minute when Kevin Nolan cut the ball back to Diouf but the Senegalese international wasted the chance by firing straight at Hoult.
Albion hit back well though and Poole was forced to make a good save to deny Andy Johnson.
The introduction of Robert Earnshaw for Kanu gave their attack another dimension as they stretched the home side's defence.
Okocha thought he had put Bolton back into the game in the 72nd minute when his 25-yard free-kick beat Hoult, only to come back off the bar.
Nolan squared another ball across the six-yard line that evaded his fellow attackers before Diouf volleyed over the bar from a good position.
Wanderers looked to have won a penalty in the 83rd minute when Nolan's shot appeared to be handled by Riccardo Scimeca but the referee was having none of it.
A minute later Bolton did finally equalise. Ivan Campo's pass picked out Nicky Hunt on the right and his cross found Diouf in space to fire past Hoult.
Okocha was foiled by Hoult as Wanderers went in search of the winner, while Nolan was also just off target with a last-ditch effort.
MAN OF THE MATCH: Ivan Campo (Bolton) - Controlled the Wanderers midfield and kept the play flowing with a fine array of passes.