The 32-year-old had to have stitches following the assault in Bridge of Weir, Renfrewshire, in the early hours of Sunday.
Police said he had been at the pub with friends and became involved in a disturbance involving a group of people on Main Street, near Chillies takeaway.
He was treated at the Royal Alexandra Hospital in Paisley for a head wound and other injuries to his face.
Detective Constable Neil Andrew said: "Officers are checking CCTV from the area and carrying out other local inquiries. However, I appeal to anyone who was in the area and saw the incident or who has any information that may assist the inquiry to contact Paisley CID or any other police officer."
In Dundee, a 25-year-old man also had to have stitches to his head following an attack in the city's Kirkton area.
Police said he was walking in Haldane Avenue near the local shops at around 1.20pm yesterday when he was approached by a man who assaulted him. Moments later he was attacked by a second man in Haldane Crescent.
He was treated at Ninewells Hospital before being released.
Detectives said there were several people in the area when the attacks happened and they want to speak to anyone who may be able to help them trace the two men.
A Police Scotland spokesman said: "Inquiries were carried out in the area yesterday, including forensic examination at the scene and house to house inquiries.
"An additional police presence is continuing in the area today as the investigation continues in an effort to gather more information and to provide reassurance to the community."