Leading thousands of people in prayer for the victims at the Vatican on Sunday, he said that they died in "another act of ferocious violence" after refusing to renounce their faith.
Speaking from his studio window overlooking St Peter's Square, the pontiff said: "May the Lord welcome these courageous witnesses, these martyrs, in his peace and convert the hearts of the violent ones."
The group was travelling from Beni Suef province to the remote monastery of St Samuel the Confessor in Maghagha when gunman opened fire on their vehicle approximately 140 miles south of Cairo. More than 20 people were injured.
During a visit to the Italian city of Genoa on Saturday, Pope Francis prayed for the victims and warned the number of martyrs today exceeds that of early Christian times.
Islamic State claimed responsibility for the incident - the fourth deadly attack targeting Christians since December last year when a suicide bomber struck a chapel next to St Mark's Coptic Orthodox Cathedral in Cairo, killing 29 people.
Meanwhile, Egyptian government fighter jets struck militant training bases in neighbouring Libya at the weekend in retaliation for the incident.
President Abdel-Fattah el-Sissi said planes have targeted sites in eastern Libya responsible for the training of those behind the shooting.