In 1662, she became Princess of Monaco. She visited Monaco in 1662, where she stayed for three years, after which she returned to the French court. The Prince and Princess of Monaco spent more time in Paris than they did in Monaco. The couple were well-established at the royal court of Louis XIV, where Catherine Charlotte held the position of lady-in-waiting to Princess Henrietta of England, sister-in-law and former lover of Louis XIV. Her aunt, Suzanne Charlotte de Gramont, marquise de Saint Chaumont, was also a member of Henrietta's household as the governess of her two daughters, Marie Louise and Anne Marie.
Catherine Charlotte's beauty did not go unnoticed. She was renowned for her beauty and wits, and attracted many lovers, including the king, the marquis de Villeroi, and her cousin, "the little Lauzun". Madame de Sévigné described her as "greedy for pleasure", and she was nicknamed Catherine the Torrent.
The king, who was losing interest in his mistress, Louise de la Vallière, began an affair with Catherine Charlotte that lasted only a few months. Catherine Charlotte's husband, Louis I, Prince of Monaco, diplomatically left court and went off to war. In reality this was part of a plot designed by Henrietta of England to distract the king from Louise so that she might gain him back for herself. Louis XIV did in fact leave Catherine Charlotte after a few months, not to go back to Henrietta, but in favor of Madame de Montespan. Some gossip has it that, during this short affair, Catherine also had an intimate relationship with Henrietta. She was forced to return to Monaco in 1668 after having been banished from court for her affairs.
In 1672, she returned to the French court, where she spent the rest of her life. Catherine Charlotte died in Paris on 4 June 1678, aged 39.