The Million Dollar Vegan campaign - run by a couple from York, offered the pontiff a donation of $1m (£771,405) for the charity of his choice if he avoids all animal products for 40 days.
The face of the campaign is twelve-year-old American animal rights and environmental campaigner Genesis Butler.
She travelled to Vatican City this week to put more pressure on Pope Francis to ditch his normal eating habits during the religious observance.
The Million Dollar Vegan campaign said in a statement: "Pope Francis is considering Genesis's plea to go vegan for Lent.
"Today Genesis attended a general audience with Pope Francis at the Vatican, following an earlier meeting inside the Vatican yesterday with senior Catholic priest Fr Pawe Ptasznik.
"It was at this meeting that Genesis spoke with such integrity and passion about her love for animals and how we need to change our behaviour to protect them and the planet that we live on.
"Father Ptasznik responded 'we are all responsible for our Earth, I agree with your words'. And he agreed to be her messenger, and to take her letter, signed by dozens of celebrities, scientists and influencers, as well as the petition signed by tens of thousands of people, and hand it to Pope Francis.
"Father Ptasznik asked for Genesis's home address and told her to await a response from the Pope.
"During today's general audience, Pope Francis acknowledged Genesis and smiled in response to her question: 'Your Holiness, will you go vegan for Lent?'."
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