One fire crew from the town's station was scrambled to The Dingle Garden in the Quarry park for a non-urgent call at 5.26pm on Sunday.
When they arrived they found two people who were locked in the landscaped garden area and could not get out. Luckily Shrewsbury Town Council staff were still in the park and were able to release them.
The Shropshire Fire & Rescue Service incident log summarised the rescue: "Two persons released from locked enclosure."
The incident was declared over at 5.36pm.
A woman who reportedly helped the couple after they were locked in the garden said they had not seen the sign saying the gates would be locked at 4pm. After talking to them by the bandstand, they said the town council offices had closed by the time they'd tried to contact the authority at 4.45pm.
She said they had to "resort to contacting the police who then contacted the fire brigade", and said the experience was "rather traumatic" for the couple.
Helen Ball, town clerk at Shrewsbury Town Council said: "The Dingle is locked daily by the Town Council’s Security staff and involves locking the four gates, walking through the site and calling out to warn people of closure.
"On this occasion no one was observed in the area.
"Security staff were however still within the park when the fire service arrived and were able to unlock the gates.
"All parted on good terms.
"Procedures have subsequently been changed to ensure this does not happen again."