Police arrived at Knightsbridge Drive to find a 56-year-old Tarneit woman with life-threatening injuries.
A neighbour said she saw the single mother being taken by ambulance and was shocked at her condition and was very concerned for her.
An ambulance spokesperson said that the woman was taken to the Royal Melbourne Hospital in a critical condition.
A 30-year-old Tarneit man was arrested at the scene and is assisting police with their enquiries.
Police believe the parties are known to each other and investigations are ongoing.
Anyone with information is urged to contact Crime Stoppers on 1800 333 000 or submit a confidential report online at www.crimestoppersvic.com.au.