The service, which is confidential and free, will be open to sufferers and their families.
The helpline has been set up by the Bluebell Campaign, which described it as “a major step forward” in providing Scotland-wide support.
The condition is thought to affect one in 10 women and can lead to feelings of despair or hopelessness.
Viv Dickenson, one of the founder members of the Bluebell Campaign, said: “Until now support for families struggling with postnatal depression has been patchy.
“It is often not just a new mum that suffers, research shows that fathers often become depressed after childbirth too or don’t know what to do when their partner becomes depressed at a time when everyone expects them to be happy.”
The initiative is a joint venture between CrossReach, the social care arm of the Church of Scotland, and the charity Children 1st.
The helpline number is: 0800 345 7457