The development agency's new emergency appeal is being supported by extreme explorer Bear Grylls.
He is calling upon the British public to help the 18 million people in West Africa affected by the crisis.
"Millions in West Africa desperately need our help in their fight for survival: it is a plight where our help can literally change their families' lives," he said.
"Join me in the ultimate survival mission to save lives. It is too important to neglect."
Tearfund said governments and international donors must do all they can to prevent a major catastrophe in the region.
The food shortages have been brought on by erratic rainfall and a surge in food prices. Many men have been forced to leave their rural communities to find work in neighbouring countries.
One woman, named only as Azourfa, has been collecting goat droppings and selling them to a local farmer to use as fertiliser, but at a fraction of the price she needs to buy millet.
She is unable to carry firewood to sell because of an injury and her husband has been away for five months after leaving their home village of Kamrey, in southern Niger, in search of work.
"I've not faced a situation as bad as this for more than five years," said the 42-year-old.
"Sometimes I collect wild leaves to prepare for food but we don't have any left after someone stole them. Those leaves would have given us food for two or three days.
"We ate yesterday but we don't have anything for today. Tomorrow, I don't know. Maybe God will provide for me so I can eat tomorrow. Neighbours used to help us if they had enough food themselves but they don't have anything for us today so we won't eat."
Azourfa has already lost one child to hunger 10 years ago. Her youngest child now is nearly two years old but is under-developed after suffering dramatic weight loss as a result of the failed harvest. She was able to receive nutritional food supplements to boost her weight.
A local organisation supported by Tearfund helped Azourfa to grow her own cabbages as part of a market garden initiative in the village.
Now, the vegetable supply has run out.
"If it wasn't for the market gardening work, the situation would be worse and I would be suffering a lot more," adds Azourfa.
"My prayer is always that God will provide us with food so I'm able to feed my children and myself. But because of the situation we are facing, I have no hope for the next harvest."
When asked if they can survive, she says: "We cannot."
Tearfund is supporting market gardening initiatives across the worst affected countries of Niger, Mali, Chad and Burkina.
Its teams are providing food rations of millet and running cash-for-work projects, as well as selling food at reduced prices and supporting grain banks.
Slanwa Gaston, Tearfund's country rep in Niger explains the desperate situation in this short film:
