Empirical data on genetic counseling outcomes in the deaf population are needed to better serve this population. This study was an examination of genetics knowledge before and after culturally and linguistically appropriate pre-test genetic counseling in a diverse deaf adult sample. Individuals ≥18 years old with early-onset sensorineural deafness were offered connexin-26/30 testing and genetic counseling. Participants completed questionnaires containing 10 genetics knowledge items at baseline and following pre-test genetic counseling. The effects of genetic counseling, prior beliefs about etiology, and participant's preferred language on genetics knowledge scores were assessed (n = 244). Pre-test genetic counseling (p = .0007), language (p < .0001), prior beliefs (p < .0001), and the interaction between counseling and beliefs (p = .035) were predictors of genetics knowledge. American Sign Language (ASL)-users and participants with "non-genetic/unknown" prior beliefs had lower knowledge scores than English-users and participants with "genetic" prior beliefs, respectively. Genetics knowledge improved after genetic counseling regardless of participants' language; knowledge change was greater for the "non-genetic/unknown" beliefs group than the "genetic" beliefs group. ASL-users' lower knowledge scores are consistent with evidence that ethnic and cultural minority groups have less genetics knowledge, perhaps from exposure and access disparities. Culturally and linguistically appropriate pre-test genetic counseling significantly improved deaf individuals' genetics knowledge. Assessing deaf individuals' prior beliefs is important for enhancing genetics knowledge.