Planned closures on the Northern Line, which would have seen Tube trains stopping early on weekday evenings through the summer, have been cancelled by Transport for London (TfL).
The Bank and High Barnet branches were due to shut at about 2130 BST on Mondays to Thursdays from next week.
Engineers are to upgrade the signalling system, which is 40 years old.
But TfL has decided to revert to a normal schedule now it has brought all of its maintenance work in-house.
On Sunday the company announced it had purchased contractor Tube Lines, which has been responsible for upgrades and repairs to the Jubilee, Northern and Piccadilly Lines.
"London Underground is working with Tube Lines to review the upgrade and hence we are cancelling the immediate early-evening closures planned," said Mike Brown, managing director of London Underground.
The priority was to agree a plan "that gets the job done to a timetable that suits Londoners, and with the minimum disruption to our customers and businesses", he added.
In March an organisation representing traders in north London, Camden Town Unlimited, warned the upgrade could lead to a loss of night-time business and force some retailers to close.
Caroline Pidgeon, the Liberal Democrats' spokeswoman for transport on the London Assembly, said she had "spoken to many small businesses and local residents and know what problems these closures would have caused".
"I hope that London Underground will now look seriously at minimising the number of closures on the Northern Line at a time when businesses are fighting to survive in this difficult economic climate."
TfL promised it would be "engaging fully with the business community" and listening to traders' views when considering how to proceed with its upgrade work.