Mariano Abril y Ostalo was born on May 25, 1861, in San Juan, Puerto Rico.
During his youth, he worked as a notary clerk while writing for El Palenque de la Juventud under the pseudonym of "Florete".
He then worked for El Clamor del País, a San Juan political newspaper.
After receiving a pardon from the Ministry of Overseas, Don Antonio Cánovas del Castillo, he remained in Madrid for three years collaborating for the newspapers El Globo, Heraldo de Madrid, and El Liberal.
When the Spanish–American War ended in 1898, he returned to Puerto Rico and joined Luis Muñoz Rivera in his political fight.