The purpose of this study was to determine whether there were differences in levels of sentence complexity and grammatical correctness between the spoken and written persuasive language of adolescents with Learning Disabilities (LDs). After viewing short videos providing background information on controversial animal welfare topics, spoken and written persuasive samples were collected from 27 adolescents with LDs. The samples were analyzed for measures of sentence complexity descriptively and quantitatively using multivariate analysis of variance. Sentences were further evaluated for percent of complex vs. simple and grammatically correct vs. incorrect productions. Complex sentences were produced with similar frequency in written (84%) and spoken (75%) persuasion. Thirty-three percent of written and twenty-six percent of spoken complex sentences contained grammatical errors. Given the social and academic value of persuasive communication and the shared grammatical weaknesses in sentences, our findings lend support to combined speaking and writing practice and use of effective collaborations between educators and speech-language pathologists when teaching the language of persuasion.