Cardinal Coislin went to court as little as he could, and was always in dispute with the king there, who even bit him sometimes; all the rest of his time he spent in his diocese, which he administered with great vigilance and by well-chosen means. He gave all the diocese's revenue [away] and made great handouts, though he always lived very honourably. Since his death, it has become known that he did major penances for many years, and that he only relaxed from them at night, when his household got undressed, to pray, and it was due to this that his last illness is attributed. Missionaries to the parish of Versailles came to him at his end and, with strange barbarism, no longer did they want to leave off approaching him as confessor; such was his domination of these people. The king wished the curé of Versailles to accompany [Pierre's] body to Orleans, an honour that has never been given to anyone since then, and of which his virtue was judged worthy. The whole diocese screamed, but these regrets were only the start of their sorrows.
this prelate was the object of a unique veneration. He was a man of average size, fat, short, a ruddy and unravelling face, an aquiline nose, handsome eyes with an air of candour, goodwill and virtue, who captivates all who see him and who touches even more those who know him [...] Of his diocese, that he took up when very young, he touched nothing and put his whole revenue into good works every year.
One of his successors removed the epitaph from the cardinal's tomb "since people were going there to pray to God, as at a saint's tomb". His nephew Henri Charles du Cambout de Coislin was also a bishop.