Pope Leo also remembered civilians caught in other conflicts, including in parts of Africa and Asia, and prayed for peace for people suffering under political instability, religious persecution and terrorism.
He urged world leaders to reject violence and indifference, stressing that peace must be rooted in justice, dialogue and solidarity with the most vulnerable.
"In becoming man, Jesus took upon himself our fragility, identifying with each one of us: with those who have nothing left and have lost everything, like the inhabitants of Gaza; with those who are prey to hunger and poverty, like the Yemeni people; with those who are fleeing their homeland to seek a future elsewhere, like the many refugees and migrants who cross the Mediterranean or traverse the American continent," the pontiff said.
"On this holy day, let us open our hearts to our brothers and sisters who are in need or in pain. In doing so, we open our hearts to the Child Jesus, who welcomes us with open arms and reveals his divinity to us," he added.
Pope Leo, the first U.S.-born pope, was elected in May following the death of Pope Francis and has made appeals for peace a central theme of his early papacy.
He has repeatedly called for an end to Russia’s war in Ukraine and has met with Ukrainian President Volodymyr Zelenskyy as part of his diplomatic outreach.
The Vatican said in July that Pope Leo expressed willingness to host representatives of both Russia and Ukraine for peace negotiations, a position he has maintained.