This study examined the effects of orofacial myofunctional therapy (OMT) on speech intelligibility in adults with persistent articulation impairments. Six adults in the age range of 18-23 years were selected to receive orofacial myofunctional therapy for a period of six weeks. The results showed that five out of six clients made significant progress in oral postures and speech sound production across all three speech production tasks: single words, sentences, and spontaneous speech. Speech intelligibility increased significantly in all clients except the one diagnosed with developmental apraxia of speech. Orofacial myofunctional therapists, speech-language pathologists, and other professionals need to rule out underlying orofacial myofunctional variables when targeting speech sounds for intervention. Speech production tasks may be considered as important measures to understand the efficacy of OMT in clinical settings.