The Latics twice came from behind before McManaman, who scored his first Barclays Premier League goal against Tottenham last weekend, swept home from close range following Shaun Maloney's superb run.
Shane Long and Gareth McAuley put West Brom ahead in the 29th and 50th minutes, only for Arouna Kone and James McArthur - with his first touch - the drag the visitors back into it.
Wigan goalkeeper Joel Robles also played an important role, saving a Graham Dorrans piledriver in the 89th minute.
- Sports & Recreation
- Shaun Maloney
- Arouna Kone
- Gareth McAuley