Hien came from a family into the Mekong Delta province of Hà Tiên. His father was a district magistrate in the nearby province of Vĩnh Long before coming home to serve as the governor of Ha Tien in the last years of the Nguyễn dynasty before French colonization. According to a family register, Hien was a quick-learner as a student in his youth, known for his abilities in mastering the classics. By the age of 20, in 1876, he was considered to be ready to enter the imperial examination system. However, southern Vietnam had been colonized by France in 1867, so his participation exams would not have had any relevance unless he was prepared to leave the south to live in the capital Huế, or some other place in the north of the country.
