Archaeologists believe they have found the foundation walls of three separate buildings on the recently demolished Beehive site on Walkergate.
They are still waiting for samples to be dated but are confident the wall nearest the road was built in the mid to late medieval period, possibly in the 16th century.
A second extant wall further in is thought to date from the 17th or 18th century, with the footing of the former Tweeddale Press buildings dating from the early 20th century nearby.
Chris Burgess, Northumberland county archaeologist, said: "It's very interesting to see the progression of the site through three phases of building which seems to show how the street has become wider over the years.
"Basically, we are probably seeing a progression from early to late from the front of the site to the back through a series of different buildings gradually moving away from Walkergate, probably as it got wider."
The team from Tyne and Wear Museums always thought the site would throw up some interesting archaeology given Berwick's history.
Terry Frain, assistant keeper of archaeology for Tyne and Wear Museums, said: "It's common knowledge there is quite a lot of archaeology stratified within the walls of Berwick so we knew for a fact there would be some good finds.
"Unlike most towns and cities which tend to spread out as they develop, the confines of a place like Berwick because of its town walls meant sites such as this were levelled and re-developed on top several times."
The land has been reworked so many times that archaeologists believe soil samples could even date as far back as the 1300's.
The team have been working on the site for five weeks and have until mid-December to complete their work before filling in to enable construction work to start on the £3.3 million creation of 30 business start-up units.
Mr Burgess said: "I hope they will continue to find good, exciting archaeology but I can't give any hard and fast advice about what they are going to find over the next few weeks.
"However, I am hoping they will be able provide a much clearer picture of the story of that site, perhaps by finding artefacts which can be used to date the walls more accurately."
Once the excavations have finished, the team will have a watching brief over the initial construction work to check for fresh archaeological information.
A webcam will be mounted on the Tweeddale Press building over the next couple of weeks to enable the public to see what is happening. A dedicated website is being set up for it, with the address to be announced soon.


e-mail: iansmith@tweeddalepress.co.uk