The Pope paused to stroke a police sniffer dog as he thanked officers for their hard work.The Pontiff praised the West Midlands Police, who deployed 2,000 officers for the final day of the state visit.
And he greeted explosives sniffer dog Jake, a black Springador, following the service at Oscott College in Sutton Coldfield.
The Pope is a known cat lover, although pets are not allowed in the Apostolic Palace, his official residence.
Assistant Chief Constable Sharon Rowe said: "It was a pleasure to meet his Holiness and very kind of him to take time to extend thanks to all the officers involved in the police operation.
"This has been a hugely complex operation. It has involved agencies from across the public and private sector and been months in the planning. I'm pleased to say it has been a resounding success.
"I would like to thank everyone involved in making the event such a memorable occasion for the tens of thousands of people who came to welcome his Holiness to our city."
An estimated 20,000 well-wishers lined Hagley Road, where just one person was arrested for a minor breach of the peace.
Afterwards at Birmingham Airport the Pope said he was "very grateful for all the hard work of preparation" done by the Government, local authorities, police and volunteers during the four-day tour.