Owner Capital Shopping Centres has announced that Merlin Entertainments will open a 36,000 sq ft attraction in the Barton Square section of the Greater Manchester retail hub.
The news comes after Trafford Metropolitan Borough Council approved a resolution to grant planning permission for a change of use of the existing floorspace.
Merlin will also operate the £6.5m aquarium attraction, its 14th in the UK, next to its Legoland Discovery Centre which opened in 2009.
The new Sea Life centre will have tanks containing more than 5,000 creatures, 30 marine displays, an underwater ocean tunnel and some as yet unannounced features.
CSC asset management director Julian Wilkinson said: "The Trafford Centre is really excited to be embarking on plans to bring such a world-class tourist attraction to our 31 million annual shoppers.
"For CSC, providing innovation to our growing leisure offer is absolutely key; the shopping centre experience is about being more interactive.
"We believe the future of successful shopping centres is inextricably linked to providing a quality leisure experience, and we have seen what Sea Life has achieved at other locations."