St Modwen is undertaking the regeneration project in partnership with Welwyn Hatfield Council and English Partnerships and will start preparation works around the former Bill Salmon Centre.
The new town centre scheme will see 45 new shops, restaurants, a multi-storey car park, library, market hall, leisure and community facilities built, as well as a bus interchange and 162 homes.
Phase one will include three new buildings of retail on the ground level and residential above.
The development was due to start in 2008, but was shelved at the start of the credit crunch by St.Modwen.
Rupert Wood, regional director for St. Modwen, said: “We are pleased to announce that works will commence in the next couple of weeks to begin building phase one of the town centre regeneration scheme.
“Over the course of the next eight to 12 weeks people will see the start of enabling works which will include site mobilisation and the carrying out of diversion works.
“We will be making further announcements as the programme is finalised.
“The work is scheduled to take 12 to 15 months.”