Around 350 people attended the party at the Lion Quays Hotel and Spa near Oswestry, where a fight broke out on the dancefloor in the early hours of Sunday morning.
West Midlands Ambulance Service was called to the scene at around 12.15am and one man was taken to the Princess Royal Hospital in Telford.
A spokesman for the ambulance service said: "We were called to the scene at 12.18am after a reports of a male being injured following a fight.
"We attended to the patient and he was taken to the Princess Royal Hospital.
"A second patient was attended to and they took themselves to hospital, and a third patient was treated at the scene."
West Mercia Police were also called to the hotel.
Sally Rogers, who attended the party, said the incident began on the dancefloor but continued outside the building.
She said: "It was a lovely evening until around midnight.
"It started on the dancefloor, only the young waiting on staff came out to help the one guy off dancefloor with a nasty head injury.
"He had blood all over his shirt, they went outside where it carried on.
"We just felt very unsafe and concerned for the young workers as well as party goers."
A spokesman for the hotel confirmed they were helping the police were their investigation.
He said: "I can confirm regrettably we had an incident at the resort on Saturday, this was defused within minutes by the team and staff here.
"This is a one-off incident and has never happened in 16 years of the business.
"Due to the investigation that is taking place we don't really want to comment any further."