At around 1.30am officers were made aware of two men in their twenties, being brought into hospital with serious injuries.
Further investigation found that the assault happened at The Dome nightclub in Grafton Gate East, Milton Keynes.
The men remain in hospital and are receiving treatment.
Investigating officer, Inspector Andy Thompson, said: “We are carrying out a thorough investigation following this incident at The Dome nightclub in Milton Keynes.
“We believe that the assault happened in the outside smoking area of the club at shortly before 1.30am.”
“We are following a number of lines of enquiry to investigate, but at this stage no arrests have been made.
“Members of the public are likely to see an increase police presence while we continue our enquiries.
“Anyone with information should contact Thames Valley Police on 101 or through our online reporting.
“Or if you do not wish to speak to police you can report 100% anonymously through the independent charity Crimestoppers on 0800 555 111.”
