"What are the nuns doing that they can't answer the phone?" Francis asked in the message he left, the recording of which was obtained by Spain's El Mundo newspaper and broadcast on Italian media Saturday.
"This is Pope Francis. I wanted to offer you greetings for the end of the year. Maybe I'll try to call again later. May God bless you," he said.
The call was placed at 11.45am on Dec 31 to the small community of Carmelite nuns of Luccena in Cordoba, Spain. Their once-large community has now dwindled to only five nuns, three of whom are from Argentina, the Pope's home country.
The Pope finally was able to reach a nun at the convent at 7.15pm to convey his best wishes, reports said.
Francis has made a habit out of calling people out of the blue, often checking in with ordinary folks who have written him about their hardships. He places the calls himself, as evidenced by the message.