A Dominican frair and local to Siena, he was introduced to Catherine through Frate Tommaso dalla Fonte, when he was 24 years old and Catherine was 21 years old. Bartolomeo Dominici grew close to Catherine and her traveling group of men and women, evidence shows that when he is absent from the group, the women love to hear about his travels and always wish him to come back. Many letters are addressed to him, and the women Catherine travelled with ( Lisa, Giovanna, Cecca, and Alessia) make notes to him after Catherine is done dictating. Occasionally he traveled with Catherine and acted as her confessor while Raymond or Tommaso dalla Fonte was absent, he is known to travel with them to Pisa, Lucca, and Avignon. As a native to Siena, he was well aware of the political situations Catherine helped solve, and he had a special relationship with her.