On 9 May 1967, he was elected Bishop of Verapaz, assuming office the following 11 August. In this position, he emphasised pastoral work among indigenous communities of Mayan peoples. During the country's on-going civil war in the 1970s, Gerardi was a strong proponent for the official recognition of Guatemala's indigenous languages, to improve the status of the indigenous peoples. He was instrumental in securing authorisation for two radio stations to broadcast in Mayan languages.