The revamp will add 40,000 sq ft (3,715 m) of retail space in an extension to the centre.
As part of the building works, Killultagh Estates will add another storey to the existing car park and will install a modern glass structure to transform the entrance.
At present, the centre covers 290,000 sq ft (27,000 sq m) and has a 14-unit retail park on site.
Connswater is anchored by supermarket giant Tesco, department store retailer Dunnes and Woolworths. Other retailers in the centre include Argos, Boots, Next, Clarks and Carphone Warehouse.
The extension work will add nine units to the centre and a food court on the first floor.
It will be done with as little disruption as possible, according to the developer, with existing retailers continuing to trade throughout the refurbishment process.
The extra space is expected to be ready by Christmas.
Agency Colliers CRE acts on behalf of Killultagh Estates and will search for retailers to fill the new units. While no new retailers have signed yet, Colliers CRE is reported to be in discussion with a number of interested parties and has said that it will seek to bring in more fashion retailers to drive footfall at Connswater.
The new units will be about 4,000 sq ft (370 sq m) – considerably bigger than the present average in the centre of about 750 sq ft (70 sq m). Colliers CRE director Mark Thallon said: “It’s an important time to be doing this. Belfast is changing and there’s been a lot more space coming up. We think it’s important that, as new schemes come on, we upgrade Connswater.”
Connswater is three miles from Belfast city centre, which has been greatly lifted by the opening in March of the 1 million sq ft (92,900 sq m) Victoria Square shopping centre.
Connswater was sold by previous owner BL Universal – a joint partnership between British Land and GUS – to Killultagh Estates for£47.3 million in 2001 and has a total of 50 shop units.