The attack on a concert in Manchester Arena killed 22 people and injured many others.
"His Holiness Pope Francis was deeply saddened to learn of the injury and tragic loss of life caused by the barbaric attack in Manchester," read a telegram sent in his name.
"And he expresses his heartfelt solidarity with all those affected by this senseless act of violence.
"He commends the generous efforts of the emergency and security personnel, and offers the assurance of his prayers for the injured, and for all who have died.
"Mindful in a particular way of those children and young people who have lost their lives, and of their grieving families, Pope Francis invokes God's blessings of peace, healing and strength upon the nation."
As is usual custom on such occasions, the telegram was signed by the number two in the Vatican hierarchy, Cardinal Pietro Parolin.