Bing met Grace Kelly on the set of their movie The Country Girl in 1954, more than a year after his first wife's death and after he had already started dating his future wife, Kathryn Grant. At first Bing objected to casting Grace in the role of his wife in the movie because he felt she was too glamorous for the part. He finally consented to her selection and by the end of the movie they were dating.
The affair between Bing and Grace apparently continued even after Bing had proposed to Kathryn. Bing postponed his wedding to Kathryn that was set for Sept. 10, 1955, apparently because of Grace. Later that year, according to Kathryn, Bing apologized to Kathryn for his fling with the future princess.
In 1962, Bing and the now Kathryn Crosby were invited to Monaco to be the guests of now Princess Grace and her husband. Kathryn wrote (in her book): "Staggering in on high heels that should have been made of glass, I felt like Cinderella in reverse, mistakenly donning her ball gown for a picnic.... There was nothing to do but to focus my charms on the prince. His attention, however, seemed fully occupied by Bing and Grace, who had broken the initial tension by the simple expedient of wrapping themselves around each other.... Bing and Grace strolled in, still with their arms about one another's waists. Absorbed in each other, they continued to chat amiably for a moment. Then, as if from an immense height, the princess deigned to take notice of the uproar.... Her Highness turned back to her admiring escort and favored him with a long, soulful Gallic look, the English translation of which seemed to be: 'See, if you'd only married me instead of the over-dressed frump who is now leaving claw marks in the arms of my Louis XVI sofa, you might have had disciplined children.'"