Police are appealing for public assistance to help locate 22-year-old Benalla man Joseph McDonald.
Homicide Squad detectives are keen to speak to McDonald in the relation to the death of his 7-week-old son.
The baby was admitted to a Benalla hospital on Friday 25 October with life-threatening injuries before being transferred to Monash Children's Hospital where he died on 30 October.
McDonald was last seen leaving Monash Children's Hospital on Clayton Road in Clayton on Wednesday 30 October about 4.30pm.
He was wearing a white t-shirt, brown pants and grey shoes.
Investigators believe McDonald may be able to assist with their enquiries and urge him to make contact with police via 000 or by attending any police station.
Police are liaising with McDonald's immediate family who are also keen to hear from him as they are concerned about his welfare.
It is believed he may be travelling from Melbourne to Benalla by public transport.
Detectives have released an image of McDonald in the hope someone may recognise him or have information on his current whereabouts.
Anyone who sights McDonald is urged to call Triple Zero (000).
Anyone with information in relation to his whereabouts is urged to contact Crime Stoppers on 1800 333 000 or make a confidential report at www.crimestoppersvic.com.au.
