Leicester City Council said it found out on Monday the Wembley Road signs had been taken from a city industrial estate and reported it to police.
The authority said it would replace the signs and investigate ways to make them more theft-resistant.
A Leicester City Council spokeswoman said: "The signs were securely attached to their frames but were removed by someone who was clearly determined to take them.
"These signs were a small way to commemorate a big year in Leicester's footballing history, so it's very disappointing that someone has spoilt things for others by taking what was meant to be a lasting reminder of Leicester City's achievement.
David Edwards, who had been responsible for the design, construction and naming of several roads on the new industrial estate in Braunstone Frith in 1969, unveiled one of the new signs last month.
Mr Edwards, 89, worked for Leicester's city engineers department when he suggested they name a new road "Wembley Road" in the hope it would bring luck to the city's football team.
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