During the serious assault, the man sustained a head injury.
The attack took place outside licensed premises on the Hillhead Road in Toomebridge at around 2 am on Sunday.
The victim was first taken to Antrim Area Hospital but was later transferred to the Royal Victoria Hospital to be treated by specialists in serious head injury.
The three men – aged 52, 24 and 20 – and are being questioned at the PACE custody suite at Musgrave PSNI Station in Belfast.
During Sunday, there were long tailbacks on the Hillhead Road while an investigation of the scene was carried out.
One lane of the Hillhead Road remains closed this morning as inquiries continue.