Arenas was born in the countryside, in Aguas Claras, Holguín Province, Cuba, and later moved to the city of Holguín. In 1963, he moved to Havana to enroll in the School of Planification and, later, in the Faculty of Letters at the Universidad de La Habana, where he studied philosophy and literature without completing a degree. The following year, he began working at the Biblioteca Nacional José Martí. While there, his talent was noticed and he was awarded prizes at Cirilo Villaverde National Competition held by UNEAC (National Union of Cuban Writers and Artists). His Hallucinations was awarded "first Honorable Mention" in 1966 although, as the judges could find no better entry, no First Prize was awarded that year.