To an envious man who laughed, he said: "Do you laugh because you are successful or because another is unfortunate ?" Whilst he was still in the charge of Messer Francesco Guinigi, one of his companions said to him: "What shall I give you if you will let me give you a blow on the nose ?" Castruccio answered: "A helmet." Having put to death a citizen of Lucca who had been instrumental in raising him to power, and being told that he had done wrong to kill one of his old friends, he answered that people deceived themselves; he had only killed a new enemy.

Castruccio praised greatly those men who intended to take a wife and then did not do so, saying that they were like men who said they would go to sea, and then refused when the time came.

He said that it always struck him with surprise that whilst men in buying an earthen or glass vase would sound it first to learn if it were good, yet in choosing a wife they were content with only looking at her.

He was once asked in what manner he would wish to be buried when he died, and answered: "With the face turned downwards, for I know when I am gone this country will be turned upside down." On being asked if it had ever occurred to him to become a friar in order to save his soul, he answered that it had not, because it appeared strange to him that Fra Lazerone should go to Paradise and Uguccione della Faggiuola to the Inferno.

He was once asked when should a man eat to preserve his health, and replied: "If the man be rich let him eat when he is hungry; if he be poor, then when he can." Seeing on of his gentlemen make a member of his family lace him up, he said to him: "I pray God that you will let him feed you also." Seeing that someone had written upon his house in Latin the words: "May God preserve this house from the wicked," he said, "The owner must never go in." Passing through one of the streets he saw a small house with a very large door, and remarked: "That house will fly through the door." He was having a discussion with the ambassador of the King of Naples concerning the property of some banished nobles, when a dispute arose between them, and the ambassador asked him if he had no fear of the king.