After finishing his formal education, Nāwahī returned to the island of Hawaii and worked as a teacher, establishing his own boarding school at Piʻihonua in 1863. Principal Lyman later hired him to become assistant principal at his alma mater, Hilo Boarding School. Although educated and heavily influenced by the American missionaries, Nāwahī remained loyal to his Hawaiian roots, as evidenced by his later political opposition to the descendants of the missionaries. According to historian Jon Kamakawiwoʻole Osorio, "he was the living promise of the Calvinist mission and an exemplar of that mission's contradictions. He was a Christian Native who was, nevertheless, a firm and lifelong opponent of annexation." Historian Noenoe K. Silva noted that "Nawahi retained his Kanaka identity while assimilating Christianity into his life and philosophy."