Approximately 1,200 voters from the Brookside area were incorrectly allowed to cast their ballots for the neighbouring Stirchley ward of Stirchley and Brookside Parish Council.
Votes had to be removed by hand after 500 people Brookside residents voted in the Stirchley ward, before the valid papers could be counted.
Returning officer David Sidaway apologised for the error, saying: “A number of voters have been asked to vote in an election where they shouldn’t have been asked."
Speaking at the count before the votes were verified, he said: “We have been identifying the votes from those people. We will go through the votes, face down, and use the serial numbers to remove them.
“During that process we will not be able to see who those people voted for.”
The confusion left some councillors baffled.
Conservative candidate Harvey Unwin said: “This is a new one for me. I have been involved in elections as an agent, candidate, and runner for 42 years, and have never seen anything like this.”
Once all valid votes were counted - and ineligible ballot papers removed - Stirchley’s two available seats were won by Cllr Unwin and fellow Conservative Tammy Wood, with 308 and 317 votes respectively.
Labour’s Ian Preece won the Dawley and Aqueduct seat while the Conservatives gained Donnington through former soldier Jay Gough.
Speaking afterwards the newly election Cllr Gough said the 2021 election campaign “just felt more positive, especially with people recognising the work I’m doing cleaning, tidying and refurbishing the war memorial; people really relate to it”.
“A lot of people told me they thought Donnington had been forgotten. I want to help do something about that.”
Cllr Preece, who was already a town councillor and deputy mayor of Great Dawley, said there was a “ceiling” on the work he could do on the lower-tier authority, and said joining the borough council meant he could do more.
“When I saw my own town struggling, I thought I needed to take the plunge and make a difference," he said.
The first Shropshire Council election results are expected on Friday evening, with more due to be declared on Saturday.