Workers cut down one of two metal arches at Cessnock this week as part of a £300 million plan to modernise the world's third oldest metro train system ahead of the 2014 Commonwealth Games.
But within hours, residents had taken to social network Twitter to demand that the missing local landmark be returned and that the sole remaining sign be left in place.
Removing the arch was branded "an act of urban vandalism" by campaigners, and posters appeared at the station calling for the second arch to be saved.
The Twitter campaign was started by local Avril Williamson and backed by Deputy First Minister and local MSP Nicola Sturgeon.
Now Strathclyde Partnership for Transport (SPT), which runs the Subway, has reversed its decision. A spokeswoman said: "SPT would like to thank the many people who took the time to tweet, email, and drum up support for the metal arches at Cessnock.
"Although the signs are not of architectural significance, it is obvious from our discussion with the campaigners that they are valued by the local community and they have a strong emotional attachment to them as part of a sense of place.
"As a result, SPT has agreed to reinstate the metal arch which has been taken down and the other will remain in place."
Architect Lachie Munro designed the arches as a homage to the famous Glasgow architect Alexander "Greek" Thomson.
He said he was "surprised and delighted" at the number of people who had rallied round in a bid to have them preserved.
Mr Munro, of Glasgow-based firm Munro Associates, said: "I could not believe it, and it's really fantastic. It's very gratifying to find out your work is appreciated by so many people.
"When I designed them the idea was to imagine what the Alexander Thomson would have created had he been alive to do so, but there was no suggestion at the time that they were so well-liked.
"An architect friend was joking with me that very few of us ever get to find out that people care about our work while we are still alive."
He added: "I'm delighted to learn they have been saved. It's not often that a public authority like SPT change their mind."