Princess Antoinette of Monaco was baptised on March 5, 1921. The ceremony took place at Monaco's Cathedral. The Bishop of Monaco conducted the ceremony and the "numbers of clergy and the splendour of their vestments were remarkable," reported the The Times of London. The Princess' parents, the Duchess of Valentinois and Prince Pierre were present for the ceremony, as were the baby's grandfather, Hereditary Prince Louis, who had come from Silesia, "where he is attached to the Plebiscite Commission), the maternal grandmother, the Marquise de Polignac, and the Prince of Monaco, who is the infant princess' great-grandfather.
The route between the Cathedral and the Palace was lined with cheering crowds. The Prince of Monaco hosted luncheon and a reception in the afternoon at the Palace. The parents received a congratulatory telegram from the Pope. The Duchess de Valentinois, "in response to the acclamation of the populace, had to appear on the balcony.
In the evening, there were musical concerts and a torchlight procession in honor of the infant princess, third in line to the Monegasque throne.