The pontiff and Monsignor Georg Gaenswein, a fellow German, embraced warmly.
Benedict, 85, held up well during the nearly three-hour long service Sunday, which also marked Epiphany, a Catholic feast day.
Gaenswein, 56, has been Benedict's closest aide for years, and helped steer the papal household through an embarrassing scandal of leaked documents last year.
A Vatican court convicted the pope's former butler, Paolo Gabriele, of stealing the documents from the papal apartment. Benedict has since pardoned him.