The new on-pack message from the supermarket will read: "Don't waste me, freeze me, in a suitable, clean container, then defrost in the fridge, use within 24 hours."
More than £150 million worth of milk is wasted each year, with milk unused by households making up 90% of this, according to waste reduction organisation Wrap.
According to a recent survey for Co-op, 66% of UK adults do not freeze milk at home, 31% did not know you could freeze it and, of these, 34% say that they will start to freeze it.
Milk is best used within one month of freezing and should be defrosted in the fridge. Once fully thawed, it should be used within 24 hours.
Catherine Dishington, environment and sustainability manager at Co-op, said: "Freezing food is one of the easiest ways to make the most out of your weekly shop and prevent food wastage but not everyone knows that it's perfectly safe to freeze milk.
"We hope that by having this message on pack it will not only save customers some money, it should also help them to throw away less."
Estelle Herszenhorn, strategic technical manager at Wrap, said: "Milk is one of the most wasted food products in the UK so this is a welcome move from the Co-op, demonstrating their commitment to helping people waste less.
"We encourage people to check out the Love Food Hate Waste website for more ways to make the most of the food you buy, save money and fight climate change."
The new messaging will appear across all Co-op own brand milk products from September 2022.