The 22-year-old, was found at an address in the Shaftesbury area of the city, with serious head injuries and was taken to the Royal Gwent Hospital.
A 46 year old man and a 37 year old woman, both from the Neath area, a 22 year old man from the Newport area and a 41 year old man from the Pontardawe area have been arrested.
Gwent Police said they were in custody and appealed for anyone with information to come forward.
The 22 year old man who was found with serious head injuries, remains in hospital in a critical condition.
Officers are urging anyone that might have noticed anything suspicious in or around Tewkesbury Walk, Evans Street, Shaftesbury Street and Glastonbury Close between 6.30pm on Thursday and 12.30am on Friday to come forward.