Prat was promoted to a lieutenant on September 9. The future hero returned to Naval School, but this time as an instructor. From 1871, he was the Second Commander of Esmeralda, leading to his appointment to several positions in the school (teacher, subdirector, internal director), and was assigned to teach courses such as Naval Order, Law, Naval Tactics and Cosmography. Additionally, he was responsible for docking the corvette for four years (1871–1874) in the port of Mejillones. He received the title of Graduated Corvette Captain (equivalent to lieutenant commander) in 1873 and Capitán de Corbeta Efectivo in 1874. He was a dedicated teacher who fought against the lack of resources available to provide quality education. He himself translated textbooks from French to Spanish.
When he learned that he would be promoted to Corvette Captain, he finally decided to ask for Carmela's hand, in 1873. The only love letter from Prat to his fiancée that has survived is dated shortly after:
On 5 May 1873 the wedding bells sounded over the San Agustín de Valparaíso church. A beautiful red carpet was laid, over which the radiant 22-year-old bride passed on her way to the altar. Her parents had died when she was a girl, and she had been raised by her siblings, through whom she had contact with the Chacón family. The Chacón adopted her as a member of the family. Tall, slender and beautiful, she met with a sturdy Arturo Prat, with large forehead due to his baldness, thick beard and steady step. The minister, José Francisco Salas, blessed them at 10:30 am. They were married. Their relationship as spouses was based on a love that did not fade during the six years they lived together. Prat treated his wife as an equal, as a partner (something really rare in that society), putting her in charge of the family budget; and he, on the other hand, helped with some house chores: "At every moment I seem to find you exhausted from rocking our daughter, without me being next to you and sharing, albeit a bit, your labors...".