Emergency crews were called to the Pride Hill area of the town shortly before 1am on Thursday to reports that a man had been assaulted.
Castle Street was closed throughout Thursday morning to all traffic from the railway station while forensic officers investigate at the scene, leading to long peak-time queues in the town.
Suggestions a man had been stabbed were rebutted by Shrewsbury police inspector Saf Ali.
"It wasn't a stabbing," he said.
"There was a fight between two people. The injuries are not as bad as first thought. We've arrested one male who is in custody. The other was taken to hospital with non life-threatening injuries."
West Mercia Police later said in a statement that a serious assault took place in the early hours, and officers had arrested a 32-year-old man.
West Midlands Ambulance Service was also called. A spokesman said: “We were called at 12.54am to reports of a patient at Pride Hill who’d been assaulted.
"We sent one ambulance to the scene. On arrival we found a man who’d suffered potentially serious injuries. He was treated on scene before being taken to hospital for further treatment.”
There were reports of congestion in Frankwell and the St Michael Street areas while Castle Street was closed.
The road reopened at around 12.30pm.
Police have appealed for anyone who may have seen the incident to contact DI Dafydd Jones on 101 with ref 19i 10 June.