"When I pray, sometimes I fall asleep," he said in an episode of a Catholic TV2000 television programme published Tuesday on Youtube.
"Saint Therese did it too," he said in reference to a 19th-century French nun, adding that Christians were called to feel like children lying in their fathers' arms - a place conducive to napping, he implies.
The 80-year-old Argentine head of the Roman Catholic Church radiates energy and enthusiasm when he meets people, but his expression turns very grave when he prays, often bowing his head and closing his eyes for long periods.
The pontiff values his sleep and is tucked up in bed each night by 9pm (2000 GMT) - though he rises with the lark at 4am (0300 GMT).
His fast-paced schedule is only possible because he gets his head down for a snooze after lunch, Vatican sources say.